BY CHRISTOPHER TENNANTSTUDENT.COM CORRESPONDENTWhen David Green gets ready to write a term paper, he boots up his computer, pulls his chair close to his desk and draws a deep breath. He crushes a tablet of Ritalin beneath a textbook, leans over his desk blotter and inhales the small mound of white powder. The Harvard sophomore says Ritalin, a concentration drug for which he does not have a prescription, helps him focus on his schoolwork. "…showed first 75 words of 1578 total…

…showed last 75 words of 1578 total…