I would be happy to recommend some sources for you to look at, but you've asked a very expansive question that could be answered a number of different ways. It would really help if you could narrow down your focus/time range somewhat.

I've left this question up because I think some flaired users may be able to help you find sources. But I'd like to remind everyone looking to respond that we have a rule on homework help. Recommending sources and pointing the OP in the right direction is fine, but please don't write the essay for him/her.