On the Characterization of Preinvex Functions.

In Refs. [J. Math. Anal. Appl. 258:287-308, 2001; J. Math. Anal. Appl. 256:229-241, 2001], Yang and Li presented a characterization of preinvex functions and semistrictly preinvex functions under a certain set of conditions. In this note, we show that the same results or even more general ones can be obtained under weaker assumptions; we also give a characterization of strictly preinvex functions under mild conditions. [ABSTRACT FROM AUTHOR]