@article{CLTM_1975_1975_1_a3,
     author = {Greub, W. H. and  Halperin, S.},
     title = {An intrinsic definition of the {Dirac} operator.},
     journal = {Collectanea mathematica},
     pages = {19-37},
     year = {1975},
     volume = {26},
     number = {1},
     zbl = {0313.53007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CLTM_1975_1975_1_a3/}
}