@article{10_4153_CJM_1996_039_6,
     author = {Fegan, H. D. and Steer, B.},
     title = {First {Order} {Operators} on {Manifolds} {With} a {Group} {Action}},
     journal = {Canadian journal of mathematics},
     pages = {758--776},
     year = {1996},
     volume = {48},
     number = {4},
     doi = {10.4153/CJM-1996-039-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1996-039-6/}
}