Bregantini D. Moment-based estimation of stochastic volatility. J Bank Financ. 2013 Dec 1;37(12):4755-64. doi: 10.1016/j.jbankfin.2013.08.008
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