Treatment of acute myeloid leukemia or myelodysplastic syndrome relapse after allogeneic stem cell transplantation with azacitidine and donor lymphocyte infusions--a retrospective multicenter analysis from the German Cooperative Transplant Study Group - Schroeder, T; Rachlis, E; Bug, G; Stelljes, M; Klein, S (Biol Blood Marrow Transplant, 2015)