Where did he get those statistics?

I noticed the author stated many different statistics. An example would be the number of hours students of different races spend watching TV and studying. I would like to know what his sources were. Some of the statistics were, in my mind, questionable. You can find statistics to back up anything you want, the question is are they valid? Before I make my posters I would like to check the numbers. Any ideas on how I can find out his sources?