@article{1250126129, author = {Conway, J.B. and Szymanski, W.}, title = {Linear combinations of hypernormal operators}, journal = {Rocky Mountain J. Math.}, volume = {18}, number = {4}, year = {1988}, pages = { 695-706}, language = {en}, url = {http://dml.mathdoc.fr/item/1250126129} }
Conway, J.B.; Szymanski, W. Linear combinations of hypernormal operators. Rocky Mountain J. Math., Tome 18 (1988) no. 4, pp. 695-706. http://gdmltest.u-ga.fr/item/1250126129/