Morgan L, Hawe E, Palmen J, Montgomery H, Humphries SE, Kitchen N. Polymorphism of the heme oxygenase-1 gene and cerebral aneurysms. Br J Neurosurg. 2005;19(4):317-21.
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