... 665.[5] W. C. Hong, On sequential spaces and a related class of spaces, Kyungpook Math. J., 40(2000), 149 - 155.[6] B. Skorulski, First countable, Sequential. and Fr´echet spaces, J. of Formalized ... Franklin, Spaces in which sequences suffice, Fund. Math., 57 (1965), 108 - 115.[3] S. P. Franklin, Spaces in which sequences suffice II, Fund. Math., 61 (1967), 51 - 56.[4] W. C. Hong, Notes on Fr´echet, ... c(C)Cc∗= c [4]1.3. Lemma. (1) ([5], Theorem 2)(C∗)(2) ([5], Theorem 4) (C∗∗∗)(C∗)(3) ([5], Corollary 6) (C∗∗)c∗[4] [5][4] [5]2. The main results(X, c) c c∗:P (X) −→...