“…In particular, when G(A) = G t (A), A is called an invertive algebra 3 (see [2], p. 14) and a topological invertible element is said to be proper (see [34], p. 323) if it is noninvertible. Properties of topologically invertible elements have been discussed in several papers, for example, in [2], [6], [8], [9], [11], [12], [15], [17], [19], [25], and [31]- [34].…”