Neiberg RH, Aickin M, Grzywacz JG, Lang W, Quandt SA, Bell RA, Arcury TA. Occurrence and co-occurrence of types of complementary and alternative medicine use by age, gender, ethnicity, and education among adults in the United States: the 2002 National Health Interview Survey (NHIS). J Altern Complement Med. 2011 Apr; 17(4):363-70.