@article{BSMF_1964__92__259_0,
     author = {Rangaswamy, K.},
     title = {On $\sum $-groups},
     journal = {Bulletin de la Soci\'et\'e Math\'ematique de France},
     pages = {259--262},
     publisher = {Soci\'et\'e math\'ematique de France},
     volume = {92},
     year = {1964},
     doi = {10.24033/bsmf.1610},
     mrnumber = {32 #5733},
     zbl = {0127.25501},
     language = {en},
     url = {http://www.numdam.org/articles/10.24033/bsmf.1610/}
}