Well, if you want to work with N:M, follow this tutorial
www.j-cook.pro/index.php/m/many-to-many
It is much better and uses the fork system
Then the last part of the workshop is not replaced yet, still it is interresting part about the google map.
But now, google map is included in JDom, so again the tutorial shows few obselete steps.
But still it is good because it explains how to build a JDom class.
I will comment more.
Also, I must say again huge thanks to Gez who has worked on the english translation of this tutorial.