Cross Product Algebras references Can someone give some references to introductory books or online notes about group algebras and cross-product algebras ?
I've already searched on Google (but only for some online notes). The purpose of this request is just to self-learning, so I'd like something at the level of an introduction, if possible with comprehensive proves of the results.
Thanks in advance :)

Siegfried Echterhoff has a very nice notes about crossed products of $C^\ast$-algebras which is available at arXiv: See here.
Besides that, I recommend the book Crossed Products of $C^*$-Algebras, by Dana Williams.
