Breckner, W. 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.