MR3714763 Reviewed Bargetz, C.(A-INSB); Nigsch, E. A.(A-WIEN-WPI); Ortner, N.(A-INSB) Convolvability and regularization of distributions. (English summary) Ann. Mat. Pura Appl. (4) 196 (2017), no. 6, 2239–2251. 46F10 (46F05)