Welch WP, Frank RG, Diehr P. Health care costs in health maintenance organizations: correcting for self-selection. Adv Health Econ Health Serv Res. 1984;5:95-128.
Welch WP, Frank RG, Diehr P. Health care costs in health maintenance organizations: correcting for self-selection. Adv Health Econ Health Serv Res. 1984;5:95-128.