[1] Yale Univ, Yale Sch Med, Dept Internal Med Digest Dis, New Haven, CT 06510 USA
[2] Univ Trieste, Dept Med Surg & Hlth Sci, Trieste, Italy
[3] Univ Cologne, Fac Med, Cologne, Germany
[4] Trieste Univ Hosp, Liver Clin, Trieste, Italy
[5] Trieste Univ Hosp, Gastroenterol & Endoscopy Unit, Trieste, Italy
[6] CUNY Bernard M Baruch Coll, Dept Math, New York, NY 10010 USA