“…The list of citations, which we have included in this article, is believed to be potentially useful for indicating some of the directions for further research and related developments on the subject-matter which we have dealt with here. In particular, the recent works by Adiga et al (see [28,39]), Cao et al [40], Chaudhary et al (see [13,21,22]), Hahn et al [25], and Srivastava et al (see [23,29,33,[41][42][43][44][45]), and by Yee [35] and Yi [31], are worth mentioning here.…”