The effect of leucovorin rescue therapy on methotrexate-induced oral mucositis in the treatment of paediatric ALL: A systematic review - Van der Beek, Jn; Oosterom, N.; Pieters, R.; de Jonge, R.; van den Heuvel-Eibrink, Mm; Heil, Sg (Critical Reviews in Oncology/Hematology, 2019)