%0 Journal Article
%A W.M. Ruess
%T Purely imaginary eigenvalues of operator semigroups.
%J Semigroup forum
%D 1995
%P 335-342
%V 51
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/SF_1995__51_1_135420/
%F SF_1995__51_1_135420