Beal EW, Lyon E, Kearney J, Wei L, Ethun CG, Black SM, Dillhoff M, Salem A, Weber SM, Tran TB, Poultsides G, Shenoy R, Hatzaras I, Krasnick B, Fields RC, Buttner S, Scoggins CR, Martin RCG, Isom CA, Idrees K, Mogal HD, Shen P, Maithel SK, Pawlik TM, Schmidt CR. Evaluating the American College of Surgeons National Surgical Quality Improvement project risk calculator: results from the U.S. Extrahepatic Biliary Malignancy Consortium. HPB (Oxford). 2017 12; 19(12):1104-1111.