diff --git a/README.md b/README.md
index f3d38bf..11c1a61 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # TI Toolkit Token Sheets
 
-Here you can find token sheets for the TI-73 and TI-83/84-series calculators to include in external projects. The sheets contain detailed information about every token in a simple XML format. Basic scripts for parsing the sheets are also included.
+Here you can find token sheets for the TI-83/84-series calculators to include in external projects. The sheets contain detailed information about every token in a simple XML format. Basic scripts for parsing the sheets are also included.
 
 ## How to Use
 
@@ -10,7 +10,7 @@ You can also manually include a download of the sheets and/or scripts as needed.
 
 ## XML Format
 
-The XML format for `8X.xml` is outlined below; `73.xml` follows a similar schema.
+The XML format for `8X.xml` is outlined below.
 
 #### Tokens
 
diff --git a/scripts/formats.py b/scripts/formats.py
index a6cb73e..9086306 100644
--- a/scripts/formats.py
+++ b/scripts/formats.py
@@ -7,7 +7,7 @@
 from .parse import OsVersion, OsVersions
 
 
-def validate(root: ET.Element, *) -> int:
+def validate(root: ET.Element) -> int:
     """
     Validates a token sheet, raising an error if an invalid component is found
 
@@ -82,6 +82,11 @@ def text(regex: str):
                 children(r"<since>(<until>)?(<lang>)+")
 
             case "since":
+                if (this_version := OsVersion.from_element(element)) < version:
+                    raise ValidationError(f"version {this_version} overlaps with {version}")
+
+                version = this_version
+                
                 # Workaround for nested defaultdict
                 all_names[version] = all_names.get(version, defaultdict(set))