@article{MZ_1971__123_171639,
     author = {Alfred Gray},
     title = {Weak {Holonomy} {Groups.}},
     journal = {Mathematische Zeitschrift},
     pages = {290--300},
     publisher = {mathdoc},
     volume = {123},
     year = {1971},
     zbl = {0222.53043},
     url = {http://geodesic.mathdoc.fr/item/MZ_1971__123_171639/}
}