Binaural beats case studies and other information on binaural beats?

I am looking for legit documented case studies done on binaural beats. Specifically studies done in the gamma frequency to improve mental activity such as memory, problem solving, and alertness. If you have any other insightful information please feel free to post. I have recently started listening to "pure binaural beats" in the gamma frequency from youtube. Is it better, worse, or same to listen to "pure" binaural beats?