Bayer AM, Danysh HE, Garvich M, Gonzalvez G, Checkley W, Alvarez M, Gilman RH. An unforgettable event: a qualitative study of the 1997-98 El Niño in northern Peru. Disasters. 2014 Apr;38(2):351-74. doi: 10.1111/disa.12046
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