Von Scheele BG, Martin RD, Gilsenan AW, Ceberg J, Andrews EB, Masica D, Alvegård T. The European postmarketing adult osteosarcoma surveillance study characteristics of patients: a preliminary report. Acta Orthop. 2009;80:67-74.
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