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@article{PIM_1964_N_S_04_18_a20, author = {Ivan Vidav}, title = {On {Idempotent} {Operators} {In} {A} {Hilbert} {Space}}, journal = {Publications de l'Institut Math\'ematique}, pages = {157 }, publisher = {mathdoc}, volume = {_N_S_04}, number = {18}, year = {1964}, url = {http://geodesic.mathdoc.fr/item/PIM_1964_N_S_04_18_a20/} }
Ivan Vidav. On Idempotent Operators In A Hilbert Space. Publications de l'Institut Mathématique, _N_S_04 (1964) no. 18, p. 157 . http://geodesic.mathdoc.fr/item/PIM_1964_N_S_04_18_a20/