Roch AM, House MG, Cioffi J, Ceppa EP, Zyromski NJ, Nakeeb A, Schmidt CM. Significance of Portal Vein Invasion and Extent of Invasion in Patients Undergoing Pancreatoduodenectomy for Pancreatic Adenocarcinoma. J Gastrointest Surg. 2016 Mar; 20(3):479-87; discussion 487.