@article{ASNSP_1968_3_22_2_331_0,
     author = {Vaisman, Izu},
     title = {The curvature groups of a space form},
     journal = {Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche},
     pages = {331--341},
     publisher = {Scuola normale superiore},
     volume = {Ser. 3, 22},
     number = {2},
     year = {1968},
     mrnumber = {231400},
     zbl = {0155.49803},
     language = {en},
     url = {http://archive.numdam.org/item/ASNSP_1968_3_22_2_331_0/}
}