Update README.md

Author: codeliner

README.md

@@ -3,6 +3,8 @@ php-ddd-cargo-sample
 
 PHP Version of the cargo sample used in Eric Evans DDD book
 
+The original cargo sample written in java can be found [here](http://dddsample.sourceforge.net/).
+
 This project is in a work in progress state. Your welcome to fork the repo and help to finish the cargo sample app for php.
 The system is based on ZF2 to get a powerful application layer out of the box and uses Doctrine2 to persist it's aggregates. 
 This would be a common combination in a large PHP project but it is not required. We want to focus on the implementation