@article{PORMA_1989__46_4_115675,
     author = {Grzaslewicz, Ryszard},
     title = {Extreme positive contractions on the {Hilbert} space},
     journal = {Portugaliae mathematica},
     pages = {341--349},
     publisher = {mathdoc},
     volume = {46},
     number = {4},
     year = {1989},
     mrnumber = {1032505},
     zbl = {0694.47029},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1989__46_4_115675/}
}