Update README.md

AnghelLeonard · web-flow · commit 01cbed0c854a · 2018-11-08T08:29:05.000+02:00
diff --git a/HibernateSpringBootManyToManyBidirectional/README.md b/HibernateSpringBootManyToManyBidirectional/README.md
@@ -8,3 +8,5 @@
      
 **Output example:**\
 ![](https://github.com/AnghelLeonard/Hibernate-SpringBoot/blob/master/HibernateSpringBootManyToManyBidirectional/sample.png)
+
+<a href="https://leanpub.com/java-persistence-performance-illustrated-guide"><p align="center"><img src="https://github.com/AnghelLeonard/Hibernate-SpringBoot/blob/master/Java%20Persistence%20Performance%20Illustrated%20Guide.jpg" height="410" width="350"/></p></a>
