Anyone that knows about marketing or advertising I need help?

I’m writing an essay about marketing and advertising. I have to explain the differences between populist and elitist strategies in advertising. I’m confident that I have the gist of the two terms however I need sources from the internet. Articles would be great. Does anyone know of a good marketing or advertising strategy/history website? BTW we are not allowed to use Wikipedia. Thank You.

Here’s a good start: the Public Relations Society of America:

http://www.prsa.org/