@article{10_4153_CJM_1991_015_7,
     author = {Bullejos, Manuel and Cegarra, Antonio M.},
     title = {A {3-Dimensional} {Non-Abelian} {Cohomology} of {Groups} {With} {Applications} to {Homotopy} {Classification} of {Continuous} {Maps}},
     journal = {Canadian journal of mathematics},
     pages = {265--296},
     year = {1991},
     volume = {43},
     number = {2},
     doi = {10.4153/CJM-1991-015-7},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1991-015-7/}
}