diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api.UnitTests/Fitnet.Contracts.Api.UnitTests.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api.UnitTests/Fitnet.Contracts.Api.UnitTests.csproj
index a7a2323d..7ff6b0cb 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api.UnitTests/Fitnet.Contracts.Api.UnitTests.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api.UnitTests/Fitnet.Contracts.Api.UnitTests.csproj
@@ -1,16 +1,19 @@
-
+
-
-
+
+
+ all
+ runtime; build; native; contentfiles; analyzers; buildtransitive
+
-
+
all
runtime; build; native; contentfiles; analyzers; buildtransitive
-
-
+
+
runtime; build; native; contentfiles; analyzers; buildtransitive
all
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api/Common/Errors/ProblemResults.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api/Common/Errors/ProblemResults.cs
index 30792684..c40c9e66 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api/Common/Errors/ProblemResults.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api/Common/Errors/ProblemResults.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Api.Common.Errors;
-using Core.Common.BussinessRules;
+using Fitnet.Common.Core.BussinessRules;
using Microsoft.AspNetCore.Http;
using static ErrorType;
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api/Fitnet.Contracts.Api.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api/Fitnet.Contracts.Api.csproj
index 58286a75..afc1c7ce 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api/Fitnet.Contracts.Api.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Api/Fitnet.Contracts.Api.csproj
@@ -17,7 +17,7 @@
-
+
\ No newline at end of file
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Application/Fitnet.Contracts.Application.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Application/Fitnet.Contracts.Application.csproj
index 1b337996..a92cabed 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Application/Fitnet.Contracts.Application.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Application/Fitnet.Contracts.Application.csproj
@@ -1,10 +1,10 @@
-
+
-
+
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyBeAttachedToActiveBindingContractRuleTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyBeAttachedToActiveBindingContractRuleTests.cs
index 4f6745b2..406ac190 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyBeAttachedToActiveBindingContractRuleTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyBeAttachedToActiveBindingContractRuleTests.cs
@@ -1,8 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.AttachAnnexToBindingContract.BusinessRules;
-using Common.Assertions.ErrorOr;
using Core.AttachAnnexToBindingContract.BusinessRules;
-using Core.Common.BussinessRules;
+using Fitnet.Common.Core.BussinessRules;
public sealed class AnnexCanOnlyBeAttachedToActiveBindingContractRuleTests
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyStartDuringBindingContractPeriodRuleTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyStartDuringBindingContractPeriodRuleTests.cs
index 852123aa..d52a4de0 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyStartDuringBindingContractPeriodRuleTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyStartDuringBindingContractPeriodRuleTests.cs
@@ -1,8 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.AttachAnnexToBindingContract.BusinessRules;
-using Common.Assertions.ErrorOr;
using Core.AttachAnnexToBindingContract.BusinessRules;
-using Core.Common.BussinessRules;
+using Fitnet.Common.Core.BussinessRules;
public sealed class AnnexCanOnlyStartDuringBindingContractPeriodRuleTests
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/Fitnet.Contracts.Core.UnitTests.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/Fitnet.Contracts.Core.UnitTests.csproj
index 1e23152c..76e8d52c 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/Fitnet.Contracts.Core.UnitTests.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/Fitnet.Contracts.Core.UnitTests.csproj
@@ -5,18 +5,22 @@
-
-
+
+
+
-
-
+
+
+ all
+ runtime; build; native; contentfiles; analyzers; buildtransitive
+
-
+
all
runtime; build; native; contentfiles; analyzers; buildtransitive
-
-
+
+
runtime; build; native; contentfiles; analyzers; buildtransitive
all
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/GlobalUsings.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/GlobalUsings.cs
index 9ec3ca40..372976d5 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/GlobalUsings.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/GlobalUsings.cs
@@ -1,3 +1,4 @@
global using ErrorOr;
+global using EvolutionaryArchitecture.Fitnet.Common.UnitTesting.Assertions.ErrorOr;
global using FluentAssertions;
global using Xunit;
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRuleTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRuleTests.cs
index fb39e1a5..b26a0db1 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRuleTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRuleTests.cs
@@ -1,8 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.PrepareContract.BusinessRules;
-using Common.Assertions.ErrorOr;
-using Core.Common.BussinessRules;
using Core.PrepareContract.BusinessRules;
+using Fitnet.Common.Core.BussinessRules;
public sealed class ContractCanBePreparedOnlyForAdultRuleTests
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/CustomerMustBeSmallerThanMaximumHeightLimitRuleTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/CustomerMustBeSmallerThanMaximumHeightLimitRuleTests.cs
index 8cfba71e..882a9abe 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/CustomerMustBeSmallerThanMaximumHeightLimitRuleTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/CustomerMustBeSmallerThanMaximumHeightLimitRuleTests.cs
@@ -1,8 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.PrepareContract.BusinessRules;
-using Common.Assertions.ErrorOr;
-using Core.Common.BussinessRules;
using Core.PrepareContract.BusinessRules;
+using Fitnet.Common.Core.BussinessRules;
public sealed class CustomerMustBeSmallerThanMaximumHeightLimitRuleTests
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/PreviousContractHasToBeSignedRuleTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/PreviousContractHasToBeSignedRuleTests.cs
index b2717dc3..48feae15 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/PreviousContractHasToBeSignedRuleTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/PrepareContract/BusinessRules/PreviousContractHasToBeSignedRuleTests.cs
@@ -1,8 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.PrepareContract.BusinessRules;
-using Common.Assertions.ErrorOr;
-using Core.Common.BussinessRules;
using Core.PrepareContract.BusinessRules;
+using Fitnet.Common.Core.BussinessRules;
public sealed class PreviousContractHasToBeSignedRuleTests
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/SignContract/BusinessRules/ContractCanOnlyBeSignedWithin30DaysFromPreparationRuleTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/SignContract/BusinessRules/ContractCanOnlyBeSignedWithin30DaysFromPreparationRuleTests.cs
index b6bb1772..33fac240 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/SignContract/BusinessRules/ContractCanOnlyBeSignedWithin30DaysFromPreparationRuleTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/SignContract/BusinessRules/ContractCanOnlyBeSignedWithin30DaysFromPreparationRuleTests.cs
@@ -1,8 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.SignContract.BusinessRules;
-using Common.Assertions.ErrorOr;
-using Core.Common.BussinessRules;
using Core.SignContract.BusinessRules;
+using Fitnet.Common.Core.BussinessRules;
public sealed class ContractCanOnlyBeSignedWithin30DaysFromPreparationRuleTests
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/SignContract/BusinessRules/ContractMustNotBeAlreadySignedRuleTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/SignContract/BusinessRules/ContractMustNotBeAlreadySignedRuleTests.cs
index c7044e9d..61ec98c5 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/SignContract/BusinessRules/ContractMustNotBeAlreadySignedRuleTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/SignContract/BusinessRules/ContractMustNotBeAlreadySignedRuleTests.cs
@@ -1,8 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.SignContract.BusinessRules;
-using Common.Assertions.ErrorOr;
-using Core.Common.BussinessRules;
using Core.SignContract.BusinessRules;
+using Fitnet.Common.Core.BussinessRules;
public sealed class ContractMustNotBeAlreadySignedRuleTests
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/TerminateBindingContract/BusinessRules/TerminationIsPossibleOnlyAfterThreeMonthsHavePassedTests.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/TerminateBindingContract/BusinessRules/TerminationIsPossibleOnlyAfterThreeMonthsHavePassedTests.cs
index c27be301..ee851340 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/TerminateBindingContract/BusinessRules/TerminationIsPossibleOnlyAfterThreeMonthsHavePassedTests.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core.UnitTests/TerminateBindingContract/BusinessRules/TerminationIsPossibleOnlyAfterThreeMonthsHavePassedTests.cs
@@ -1,8 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.UnitTests.TerminateBindingContract.BusinessRules;
-using Common.Assertions.ErrorOr;
-using Core.Common.BussinessRules;
using Core.TerminateBindingContract.BusinessRules;
+using Fitnet.Common.Core.BussinessRules;
using TerminationIsPossibleOnlyAfterThreeMonthsHavePassed.TestData;
public sealed class TerminationIsPossibleOnlyAfterThreeMonthsHavePassedTests
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyBeAttachedToActiveBindingContractRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyBeAttachedToActiveBindingContractRule.cs
index 1a6003c9..b4f2e2a5 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyBeAttachedToActiveBindingContractRule.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyBeAttachedToActiveBindingContractRule.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.AttachAnnexToBindingContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
internal sealed class AnnexCanOnlyBeAttachedToActiveBindingContractRule : IBusinessRule
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyStartDuringBindingContractPeriodRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyStartDuringBindingContractPeriodRule.cs
index cc8966fd..3d93df01 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyStartDuringBindingContractPeriodRule.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/AttachAnnexToBindingContract/BusinessRules/AnnexCanOnlyStartDuringBindingContractPeriodRule.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.AttachAnnexToBindingContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
internal sealed class AnnexCanOnlyStartDuringBindingContractPeriodRule : IBusinessRule
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/BindingContract.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/BindingContract.cs
index 96c13e56..632850eb 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/BindingContract.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/BindingContract.cs
@@ -1,7 +1,7 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core;
using AttachAnnexToBindingContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
using DomainDrivenDesign.BuildingBlocks;
using SignContract;
using TerminateBindingContract;
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/BusinessErrors.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/BusinessErrors.cs
deleted file mode 100644
index 100d51be..00000000
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/BusinessErrors.cs
+++ /dev/null
@@ -1,7 +0,0 @@
-namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.Common.BussinessRules;
-
-public static class BusinessRuleError
-{
- public const int Type = 100;
- public static Error Create(string code, string description) => Error.Custom(Type, code, description);
-}
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/BusinessRuleValidator.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/BusinessRuleValidator.cs
deleted file mode 100644
index 5b3972de..00000000
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/BusinessRuleValidator.cs
+++ /dev/null
@@ -1,14 +0,0 @@
-namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.Common.BussinessRules;
-
-public static class BusinessRuleValidator
-{
- public static ErrorOr Validate(params IBusinessRule[] rules)
- {
- var errors = rules
- .Where(rule => !rule.IsMet())
- .Select(rule => rule.Error)
- .ToList();
-
- return errors.Count != 0 ? (ErrorOr)errors : new Success();
- }
-}
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/IBusinessRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/IBusinessRule.cs
deleted file mode 100644
index a768554c..00000000
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Common/BussinessRules/IBusinessRule.cs
+++ /dev/null
@@ -1,8 +0,0 @@
-namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.Common.BussinessRules;
-
-public interface IBusinessRule
-{
- bool IsMet();
-
- Error Error { get; }
-}
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Contract.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Contract.cs
index a0e219f6..472a8a1d 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Contract.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Contract.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
using DomainDrivenDesign.BuildingBlocks;
using PrepareContract;
using PrepareContract.BusinessRules;
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Fitnet.Contracts.Core.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Fitnet.Contracts.Core.csproj
index 3e9cfee1..1765bc7e 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Fitnet.Contracts.Core.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/Fitnet.Contracts.Core.csproj
@@ -6,7 +6,7 @@
-
+
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRule.cs
index cc0f6139..a0c1dcf6 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRule.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/ContractCanBePreparedOnlyForAdultRule.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.PrepareContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
internal sealed class ContractCanBePreparedOnlyForAdultRule : IBusinessRule
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/CustomerMustBeSmallerThanMaximumHeightLimitRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/CustomerMustBeSmallerThanMaximumHeightLimitRule.cs
index 49bafb91..0a3346fd 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/CustomerMustBeSmallerThanMaximumHeightLimitRule.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/CustomerMustBeSmallerThanMaximumHeightLimitRule.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.PrepareContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
internal sealed class CustomerMustBeSmallerThanMaximumHeightLimitRule : IBusinessRule
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/PreviousContractHasToBeSignedRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/PreviousContractHasToBeSignedRule.cs
index 888ee22f..a286274f 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/PreviousContractHasToBeSignedRule.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/PrepareContract/BusinessRules/PreviousContractHasToBeSignedRule.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.PrepareContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
internal sealed class PreviousContractHasToBeSignedRule : IBusinessRule
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/SignContract/BusinessRules/ContractCanOnlyBeSignedWithin30DaysFromPreparationRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/SignContract/BusinessRules/ContractCanOnlyBeSignedWithin30DaysFromPreparationRule.cs
index 629a540a..8dec6b35 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/SignContract/BusinessRules/ContractCanOnlyBeSignedWithin30DaysFromPreparationRule.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/SignContract/BusinessRules/ContractCanOnlyBeSignedWithin30DaysFromPreparationRule.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.SignContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
internal sealed class ContractCanOnlyBeSignedWithin30DaysFromPreparationRule : IBusinessRule
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/SignContract/BusinessRules/ContractMustNotBeAlreadySignedRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/SignContract/BusinessRules/ContractMustNotBeAlreadySignedRule.cs
index a73049ef..04ab50f2 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/SignContract/BusinessRules/ContractMustNotBeAlreadySignedRule.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/SignContract/BusinessRules/ContractMustNotBeAlreadySignedRule.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.SignContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
internal sealed class ContractMustNotBeAlreadySignedRule(bool signed) : IBusinessRule
{
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/TerminateBindingContract/BusinessRules/TerminationIsPossibleOnlyAfterThreeMonthsHavePassedRule.cs b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/TerminateBindingContract/BusinessRules/TerminationIsPossibleOnlyAfterThreeMonthsHavePassedRule.cs
index ea3f235c..4d75ecb6 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/TerminateBindingContract/BusinessRules/TerminationIsPossibleOnlyAfterThreeMonthsHavePassedRule.cs
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Core/TerminateBindingContract/BusinessRules/TerminationIsPossibleOnlyAfterThreeMonthsHavePassedRule.cs
@@ -1,6 +1,6 @@
namespace EvolutionaryArchitecture.Fitnet.Contracts.Core.TerminateBindingContract.BusinessRules;
-using Common.BussinessRules;
+using Common.Core.BussinessRules;
internal sealed class TerminationIsPossibleOnlyAfterThreeMonthsHavePassedRule(DateTimeOffset bindingFrom, DateTimeOffset terminatedAt)
: IBusinessRule
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Infrastructure/Fitnet.Contracts.Infrastructure.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Infrastructure/Fitnet.Contracts.Infrastructure.csproj
index 41538576..cbc5bed9 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Infrastructure/Fitnet.Contracts.Infrastructure.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.Infrastructure/Fitnet.Contracts.Infrastructure.csproj
@@ -5,12 +5,12 @@
-
-
+
+
-
-
+
+
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.IntegrationEvents/Fitnet.Contracts.IntegrationEvents.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.IntegrationEvents/Fitnet.Contracts.IntegrationEvents.csproj
index 5e82908c..c353dad8 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.IntegrationEvents/Fitnet.Contracts.IntegrationEvents.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.IntegrationEvents/Fitnet.Contracts.IntegrationEvents.csproj
@@ -4,6 +4,6 @@
1.0.7
-
+
\ No newline at end of file
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.IntegrationTests/Fitnet.Contracts.IntegrationTests.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.IntegrationTests/Fitnet.Contracts.IntegrationTests.csproj
index 68cd8671..5a39d64e 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.IntegrationTests/Fitnet.Contracts.IntegrationTests.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts.IntegrationTests/Fitnet.Contracts.IntegrationTests.csproj
@@ -5,9 +5,9 @@
-
-
-
+
+
+
diff --git a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts/Fitnet.Contracts.csproj b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts/Fitnet.Contracts.csproj
index 9cf27f8d..706d105c 100644
--- a/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts/Fitnet.Contracts.csproj
+++ b/Chapter-4-applying-tactical-domain-driven-design/Fitnet.Contracts/Src/Fitnet.Contracts/Fitnet.Contracts.csproj
@@ -5,9 +5,9 @@
-
+
-
+