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@article{JRAM_1976__281_151683, author = {Erich W. Ellers}, title = {The length of a unitary transformation.}, journal = {Journal f\"ur die reine und angewandte Mathematik}, pages = {1--5}, publisher = {mathdoc}, volume = {281}, year = {1976}, zbl = {0324.20054}, url = {http://geodesic.mathdoc.fr/item/JRAM_1976__281_151683/} }
Erich W. Ellers. The length of a unitary transformation.. Journal für die reine und angewandte Mathematik, Tome 281 (1976), pp. 1-5. http://geodesic.mathdoc.fr/item/JRAM_1976__281_151683/