We prove that a result of Ćirić and Prešić [Acta Math. Univ. Comenianae, 76 (2007), 143-147, Theorem 2, p. 144] has been for the first time proved before 31 years in Tasković [Publ. Inst. Math., 34 (1976), 231-242, Theorem 3, p. 238]. But the authors neglected and ignored this historical fact.