I don't go further than Wikipedia, simply because I'm not interested in authenticity. My goal is usually to find base ideas that I can change to suit my own imagination. I'm aware that this might be culturally insensitive, but I'm writing total fiction in alternate realities, it can be whatever I want.
But. If I were to write a paper, or do a serious work of historical fiction then I'd definitely do more in depth research. Honestly though, I wouldn't write something like that, because I'm not really interested in it.
Then there's the other part...I find research to be tedious and I just don't want to spend much time on it. This annoys my wife, who is a history major xD.