HMO marketing and selection bias: are TEFRA HMOs skimming?

Lepkowski, James M; Thomas, Justin; Lichtenstein, Richard L; Watkins, B; Puto, C; Adams-Watson, J; Simone, B; Vest, D. (1992). HMO marketing and selection bias: are TEFRA HMOs skimming?. Medical care. 30(4), 329-346.