@article{MAN_1953__126_160343,
     author = {T. Kato},
     title = {On {Some} {Approximate} {Methods} {Concerning} the {Operators} {T*} {T} .},
     journal = {Mathematische Annalen},
     pages = {253--262},
     publisher = {mathdoc},
     volume = {126},
     year = {1953},
     zbl = {0051.09203},
     url = {http://geodesic.mathdoc.fr/item/MAN_1953__126_160343/}
}