Lipschitzian generalized differential equations C. J. Himmelberg; F. S. Van Vleck — 1972 Rendiconti del Seminario Matematico della Università di Padova
An extension of Brunovský's Scorza-Dragoni type theorem for unbounded set-valued functions Charles J. Himmelberg; F. S. Van Vleck — 1976 Mathematica Slovaca