TY - JOUR T1 - THE ABFM BEGINS TO USE DIFFERENTIAL ITEM FUNCTIONING JF - The Annals of Family Medicine JO - Ann Fam Med SP - 578 LP - 579 DO - 10.1370/afm.1587 VL - 11 IS - 6 AU - Thomas R. O’Neill AU - Michael R. Peabody AU - James C. Puffer Y1 - 2013/11/01 UR - http://www.annfammed.org/content/11/6/578.abstract N2 - ER -