@article{GDZPPN002221993, title = {Inequalities for Powers of Unbounded Operators.}, journal = {Manuscripta mathematica}, volume = {29}, year = {1979}, pages = {71-80}, zbl = {0412.47017}, url = {http://dml.mathdoc.fr/item/GDZPPN002221993} }
Protter, M.H. Inequalities for Powers of Unbounded Operators.. Manuscripta mathematica, Tome 29 (1979) pp. 71-80. http://gdmltest.u-ga.fr/item/GDZPPN002221993/