Bailey DB, Raspa M, Bishop E, Mitra D, Wheeler A, Sacco P. Health and economic consequences of Fragile X syndrome for caregivers. J Dev Behav Pediatr. 2012 Nov 1;33(9):705-12.
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