Update README.md

Author: hantsy

README.md

@@ -3,6 +3,8 @@ angularjs-springmvc-sample-boot
 
 An example application using AnguarJS/Bootstrap as frontend and Spring MVC as REST API producer.
 
+**More details about the codes, please read the online GitBook: [Building REST APIs with Spring MVC](https://hantsy.gitbooks.io/build-a-restful-app-with-spring-mvc-and-angularjs/content/).**
+
 This version improved the original version, including:
 
 * Introduction of Gulp build system to processing the static resources
@@ -80,4 +82,4 @@ Get a copy of the source codes into your local system.
 3. Go to [http://localhost:9000](http://localhost:9000) to test it. 
 
 If you want to explore the REST API docs online, there is a *Swagger UI* configured for visualizing the REST APIs, just go to [http://localhost:9000/swagger-ui.html](http://localhost:9000/swagger-ui.html).
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