Hibernate Merge

1. http://stackoverflow.com/questions/1069992/jpa-entitymanager-why-use-persist-over-merge?rq=1
2. http://techblog.bozho.net/how-does-merge-work-in-jpa-and-hibernate/
3. https://hibernate.atlassian.net/browse/HHH-5855
4. https://github.com/hibernate/hibernate-orm/pull/1212
5. http://www.programmingforfuture.com/2011/02/hibernate-merge-may-insert-new-record.html
6. https://gopinathb4u.wordpress.com/2011/07/26/duplicate-child-inserts-during-merge-operation-in-hibernate/

Hibernate Tutorial

https://vladmihalcea.com/tutorials/hibernate/