  In a 1983 paper, Yannelis-Prabhakar rely on Michael's selection theorem to
guarantee a continuous selection in the context of the existence of maximal
elements and equilibria in abstract economies. In this tribute to Nicholas
Yannelis, we root this paper in Chapter II of Yannelis' 1983 Rochester Ph.D.
dissertation, and identify its pioneering application of the paracompactness
condition to current and ongoing work of Yannelis and his co-authors, and to
mathematical economics more generally. We move beyond the literature to provide
a necessary and sufficient condition for upper semi-continuous local and global
selections of correspondences, and to provide application to five domains of
Yannelis' interests: Berge's maximum theorem, the Gale-Nikaido-Debreu lemma,
the Gale-McKenzie survival assumption, Shafer's non-transitive setting, and the
Anderson-Khan-Rashid approximate existence theorem. The last resonates with
Chapter VI of the Yannelis' dissertation.
