Probiotic Escherichia coli Nissle 1917 (EcN) for Successful Remission Maintenance of Ulcerative Colitis in Children and Adolescents: an Open-Label Pilot Study - Henker, J; Müller, S; Laass, M W; Schreiner, A; Schulze, J (Zeitschrift für Gastroenterologie, 2008)