Lehmann K, Radbruch L, Gockel HH, Neighbors D, Nuyts G. Costs of opioid therapy for chronic nonmalignant pain in Germany: an economic model comparing transdermal fentanyl (Duragesic) with controlled release morphine. Eur J Health Econ. 2002;3:111-9. doi: 10.1007/s10198-002-0097-6.
Johannes CB, Avis NA. Gender differences in sexual activity among mid-aged adults in Massachusetts. Maturitas. 1997 Apr;26(3):175-84.