TY  - JOUR
AU  - W.M. Ruess
TI  - Purely imaginary eigenvalues of operator semigroups.
JO  - Semigroup forum
PY  - 1995
SP  - 335
EP  - 342
VL  - 51
IS  - 1
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/SF_1995__51_1_135420/
ID  - SF_1995__51_1_135420
ER  -