Breckner, Wolfgang W. “ Continuity of Generalized Convex and Generalized Concave Set-Valued Functions”.
Rev. Anal. Numér. Théor. Approx.
, vol. 22, no. 1, Feb. 1993, pp. 39-51,
https://ictp.acad.ro/jnaat/journal/article/view/1993-vol22-no1-art3
.