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@article{NUMA_1965__7_131669, author = {F.L. BAUER}, title = {An {Elementary} {Proof} of the {Hopf} {Inequality} for {Positive} {Operators.}}, journal = {Numerische Mathematik}, pages = {331--337}, publisher = {mathdoc}, volume = {7}, year = {1965}, zbl = {0148.38103}, url = {http://geodesic.mathdoc.fr/item/NUMA_1965__7_131669/} }
F.L. BAUER. An Elementary Proof of the Hopf Inequality for Positive Operators.. Numerische Mathematik, Tome 7 (1965), pp. 331-337. http://geodesic.mathdoc.fr/item/NUMA_1965__7_131669/