“…Restrictions on transformations can be weakened in two directions. We admit that transformations of the variables t , x and u can depend on arbitrary elements (the prefix "generalized" [35]), and this dependence are not necessarily point and have to become point with respect to (t, x, u) after fixing values of arbitrary elements. The explicit form of the new arbitrary elements (f ,g,h,m) is determined via (t, x, u, f, g, h, m) in some nonfixed (possibly, nonlocal) way (the prefix "extended").…”