Spring, JPA and using managed datasources with Tomcat

I was struggling for a few weeks now to get managed datasources in Tomcat6 to work with Spring and JPA. Well, finally it seems I have found a solution (I cannot prove it, because I did not implement it yet, but it looks good to me so far).
I have found two blogs covering this issue you might want to check out:

1. http://turgayzengin.blogspot.com/2007/09/multiple-persistence-units-with-spring.html
2. http://asrijaffar.blogspot.com/2007/02/spring-jpa-tomcat.html