“…A function f : X × Y → Z is called a KC-function if it is quasi-continuous with respect to the first variable and continuous with respect to the second variable. A few mathematicians studied points of joint continuity of KC-functions see, e.g., [3,6,10,16,17,20,22,23] and the survey paper of Neubrunn [25]). In particular, Piotrowski [26] proved the following result.…”