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
Rothman KJ, Wepsic JG. Side of facial pain in trigeminal neuralgia. J Neurosurg. 1974 Jan 1;40(4):514-6.