diff --git a/README.md b/README.md
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 			* [Read consistency](#workflow-scale-read-consistency)
 			* [Tradeoffs between availability and consistency](#workflow-scale-tradeoff-availability-consistency)
 			* [Tradeoffs between latency and durability](#workflow-scale-tradeoff-latency-durability)
-* [File system design](#file-system-design)
-* [Database design](#database-design)
-	- [Read-only Key-value](#database-design-key-value)
-	- [Read write key-value](#database-design-read-write-key-value)
-* [MapReduce](#map-reduce)
-	- [Anagram](#map-reduce-anagram)
-	- [TopK](#map-reduce-topk)	
-* [Web system](#web-system)
-	- [Typeahead](#web-system-type-ahead)
-	- [TinyURL](#web-system-tiny-url)
-* [Message](#newsfeed)
-	- [Twitter](#newsfeed-twitter)
-	- [Messenger](#newsfeed-messenger)
-* [Location based service](#location-based-service)
-* [User system](#user-system)
-* [Multithreading](#multithreading)
-	- [Thread-safe producer and consumer](#multithreading-thread-safe-producer-and-consumer)
-	- [Delayed scheduler](#multithreading-delayed-scheduler)
 * [Technologies](#technologies)
 	- [Minification](#technologies-minification)
 	- [Cassandra](#cassandra)
diff --git a/databaseDesign.md b/databaseDesign.md
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+# Database system
+* [Read-only Key-value](#database-design-key-value)
+* [Read write key-value](#database-design-read-write-key-value)
diff --git a/fileSystemDesign.md b/fileSystemDesign.md
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+# File system
diff --git a/locationBasedService.md b/locationBasedService.md
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+# Location-based service
diff --git a/mapReduce.md b/mapReduce.md
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+# MapReduce
+* [TopK](#map-reduce-topk)	
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diff --git a/multiThreading.md b/multiThreading.md
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+# Multithreading
+* [Thread-safe producer and consumer](#multithreading-thread-safe-producer-and-consumer)
+* [Delayed scheduler](#multithreading-delayed-scheduler)
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diff --git a/newsFeed.md b/newsFeed.md
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+# NewsFeed system 
+* [Twitter](#newsfeed-twitter)
+* [Messenger](#newsfeed-messenger)
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diff --git a/recommendationSystem.md b/recommendationSystem.md
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+# Recommendation system
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diff --git a/userSystem.md b/userSystem.md
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+# User system
diff --git a/webSystem.md b/webSystem.md
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+# Web systems
+* [Typeahead](#web-system-type-ahead)
+* [TinyURL](#web-system-tiny-url)
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