A good resource on second lien investing?

[Gil Ganz]

So far I have been looking exclusively into 1st liens (mostly non-performing), started to think about checking out 2nds as well. Is there a good resource that focuses just on this topic that someone can recommend? Can be a book, workshop, virtual training. 

[Charles Campbell]

There are many successful note investors in 2nds here on BP. 

@Martin Saenz is well known and offers training and mentoring specifically for 2nds.