%0 Journal Article
%A S. Tymowski
%T On the analogue of the formula cos \(t = \frac{1}{2} e^{it} + \frac{1}{2} e^{-it}\) for operator cosine functions
%J Commentationes Mathematicae
%D 1983
%P  173-182
%V 23
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/articles/10.14708/cm.v23i1.6051/
%R 10.14708/cm.v23i1.6051
%G pl
%F 10_14708_cm_v23i1_6051