“…Apart from the study of the usual (Lipschitz) metric regularity, Hölder metric regularity or more generally nonlinear metric regularity have been studied over the years 1980 − 1990s by several authors, including for example Borwein and Zhuang [1], Frankowska [16], Penot [25], and recently, for instance, Frankowska and Quincampoix [17], Ioffe [26], Li and Mordukhovich [27], Oyang and Mordukovhich [28].…”