@article{10_1017_S0017089500032675,
     author = {R.-Grandjean, A. and Ladra, M.},
     title = {On totally free crossed modules},
     journal = {Glasgow mathematical journal},
     pages = {323--332},
     year = {1998},
     volume = {40},
     number = {3},
     doi = {10.1017/S0017089500032675},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500032675/}
}