@article{GDZPPN001257595, title = {Semigroups of operators and second-order Cauchy problems.}, journal = {Semigroup forum}, volume = {31}, year = {1985}, pages = {297-304}, zbl = {0557.47028}, url = {http://dml.mathdoc.fr/item/GDZPPN001257595} }
Dorroh, J.R. Semigroups of operators and second-order Cauchy problems.. Semigroup forum, Tome 31 (1985) pp. 297-304. http://gdmltest.u-ga.fr/item/GDZPPN001257595/