diff --git a/Assert.thy b/Assert.thy
index 7d4bb0f..4b8950a 100644
--- a/Assert.thy
+++ b/Assert.thy
@@ -28,6 +28,21 @@
  * Dependencies: None
  ***********************************************************************************)
 
+(***********************************************************************************
+
+# Changelog
+
+This comment documents all notable changes to this file in a format inspired by 
+[Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres 
+to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [1.0.0] - 2018-06-16
+- Initial release
+
+***********************************************************************************)
+
 chapter\<open>An Assertion Framework for Isabelle\<close>
 theory
   "Assert"
diff --git a/Hiding_Type_Variables.thy b/Hiding_Type_Variables.thy
index f79fcbd..b55229c 100644
--- a/Hiding_Type_Variables.thy
+++ b/Hiding_Type_Variables.thy
@@ -29,6 +29,21 @@
  *                     not required for providing the functionality of this hack)
  ***********************************************************************************)
 
+(***********************************************************************************
+
+# Changelog
+
+This comment documents all notable changes to this file in a format inspired by 
+[Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres 
+to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [1.0.0] - 2017-06-25
+- Initial release
+
+***********************************************************************************)
+
 chapter\<open>Using Print and Parse Translations for Hiding Type Variables\<close>
 theory
   "Hiding_Type_Variables"
diff --git a/Nano_JSON.thy b/Nano_JSON.thy
index 742016e..e4638c9 100644
--- a/Nano_JSON.thy
+++ b/Nano_JSON.thy
@@ -29,6 +29,21 @@
  *                     not required for providing the functionality of this hack)
  ***********************************************************************************)
 
+(***********************************************************************************
+
+# Changelog
+
+This comment documents all notable changes to this file in a format inspired by 
+[Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres 
+to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [1.0.0] - 2019-01-21
+- Initial release
+
+***********************************************************************************)
+
 chapter\<open>An Import/Export of JSON-like Formats for Isabelle/HOL\<close>
 theory
   "Nano_JSON"