Comments on some recent methods for the simultaneous determination of polynomial zeros

In this note we give some comments on the recent results concerning a simultaneous method of the fourth-order for finding complex zeros in circular interval arithmetic. The main discussion is directed to a rediscovered iterative formula and its modification, presented recently in (Sun and Kosmol (J. Comput. Appl. Math. 130 (2001) 293)). The presented comments include some critical parts of the papers (Jpn. J. Indust. Appl. Math. 15 (1998) 295) and (Sun and Kosmol, 2001) which treat the same subject.