“…Caristi's fixed point theorem [3, Theorem (2.1)'] and its equivalent Ekeland's vaxiational principle [6, Theorem 1.1], which was not basically formulated as a fixed point theorem, and is an abstraction of a lemma of Bishop and Phelps [1] (see also [2]), have been of continuing interest in fixed point theory because of their numerous applications (see [4], [5], [8]- [10], [14]- [17]). Recently Jung et.…”