[14] Naziri-Kordkandi, A., Zohri, A., Ershad, F., Yousefi, B.: 
Continuity in fundamental locally multiplicative topological algebras. Int. J. Nonlinear Anal. Appl. 12 (2021), 129-141. 
DOI 10.22075/ijnaa.2019.13751.1715[15] Rudin, W.: 
Functional Analysis. McGraw-Hill Series in Higher Mathematics. McGraw-Hill, New York (1973). 
MR 365062 | 
Zbl 0253.46001[16] Vukman, J.: 
An identity related to centralizers in semiprime rings. Commentat. Math. Univ. Carol. 40 (1999), 447-456. 
MR 1732490 | 
Zbl 1014.16021