SAKAI Katsuro, UEHARA Shigenori. On the structure of the space of lower semi-continuous functions. Commentations Mathematicae universitatis Mathematicae Carolinae. 2006. 47. 113-126
Spaces of upper semi-continuous multi-valued functions which are absolute retracts. Bull. of the Polish Acad. of Sci., Math. 2003. 51. 319-328