@article{GDZPPN002409933, title = {Weak Holonomy Groups.}, journal = {Mathematische Zeitschrift}, volume = {121}, year = {1971}, pages = {290-300}, zbl = {0222.53043}, url = {http://dml.mathdoc.fr/item/GDZPPN002409933} }
Gray, Alfred. Weak Holonomy Groups.. Mathematische Zeitschrift, Tome 121 (1971) pp. 290-300. http://gdmltest.u-ga.fr/item/GDZPPN002409933/