Smith VK, Evans MF, Banzhaf HS, Poulos C. Can weak substitution be rehabilitated? Environ Resour Econ (Dordr). 2010 Feb 1;45(2):203-21.
Bray JW, Davis KL, Graver L, Schroeder D, Buck JA, Dilonardo J, Vandivort R. Mental health and substance abuse treatment utilization among individuals served by multiple public agencies in 3 states. J Behav Health Serv Res. 2005 Jan 1;32(3):282-93.
Mansfield CA. Despairing over disparities: an empirical analysis of the relationship between willingness-to-pay and willingness-to-accept. Environ Resour Econ (Dordr). 1999;13(2):219-34.
Williams VSL. The "unbiased" anchor: bridging the gap between DIF and item bias. Appl Meas Educ. 1997;10(3):253-67. doi: 10.1207/s15324818ame1003_4