“…In such a case we write f (x) = U (x + i0). If f (x) = U (x + i0) and f (x 0 ) = γ, distributionally, then U (z) → γ as z → x 0 , in an angular (or nontangential) fashion [4,9,27,39]; however, the converse is not true in general [8]. In the case of boundary values of analytic functions, we have the following Tauberian theorem [41].…”