README.md in groupdocs-1.5.3 vs README.md in groupdocs-1.5.4

- old
+ new

@@ -51,9 +51,11 @@
 
 ### Documentation
 
 Reference to [this page](http://rubydoc.info/gems/groupdocs) for docs and examples.
 
+There is rather exhaustive documentation about internal SDK structure at [wiki page](https://github.com/groupdocs/groupdocs-ruby/wiki/Documentation-&-Guide).
+
 There are also some examples in [repository](https://github.com/groupdocs/groupdocs-ruby/tree/master/examples) and on [wiki](https://github.com/groupdocs/groupdocs-ruby/wiki)
 
 ### Entities
 
 All entities can be initialized in several ways.