Pring CM, Skelding-Millar L, Goodall RJ. Expectant treatment or cholecystectomy after endoscopic retrograde cholangiopancreatography for choledocholithiasis in patients over 80 years old? Surg Endosc. 2005 Mar;19(3):357-60.
Dysktra LA, Granger AL. Interactions between the delta agonist SNC80, and the mu agonists, morphine, buprenorphine, and butorphanol in squirrel monkeys. Nida Res Monogr. 2000;180:65.
Gfroerer J, Lessler J, Parsley (Edwards) T. Studies of nonresponse and measurement error in the national household survey on drug abuse. Nida Res Monogr. 1997;167:273-95.