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
Caso P, Sutherland GR, Fleming A, McDicken WN. Doppler tissue imaging: current status and future prospects. G Ital Cardiol. 1995 May 1;25(5):639-47.