@article{PORMA_1956__15_2_114768,
     author = {Is\'eki, Kiyoshi},
     title = {Generalisation of a theorem by {S.} {Schwarz} on semigroup},
     journal = {Portugaliae mathematica},
     pages = {71--72},
     publisher = {mathdoc},
     volume = {15},
     number = {2},
     year = {1956},
     zbl = {0073.01102},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1956__15_2_114768/}
}