The Ekeland's variational principle for vector-valued multifunctions. Rozoveanu, P. (2000) APPS. Applied Sciences
The multi-morphisms and their properties and applications Mirosław Ślosarski (2015) Annales Universitatis Paedagogicae Cracoviensis. Studia Mathematica In this paper a new class of multi-valued mappings (multi-morphisms) is defined as a version of a strongly admissible mapping, and its properties and applications are presented.