Urgent: more info on Soap Extensions 30-720

Question

Hi. I have one week till the 70-320 test (Web services C#). I've used the MS MCAD/MCSD 70-320 book which is not bad, but does not go deep enough with some topics. One of the topics that are on the downsides for this book is the Soap Extensions for Web Services. I need some more information on that in a form of an article, and not in the form of a F1 help. Any ideas? Thanks.