Voir la notice de l'article provenant de la source eLibrary of Mathematical Institute of the Serbian Academy of Sciences and Arts
@article{PIM_1980_N_S_27_41_a29, author = {Marica D. Pre\v{s}i\'c}, title = {On {Free} {Commutative} {Groupoids}}, journal = {Publications de l'Institut Math\'ematique}, pages = {209 }, publisher = {mathdoc}, volume = {_N_S_27}, number = {41}, year = {1980}, url = {http://geodesic.mathdoc.fr/item/PIM_1980_N_S_27_41_a29/} }
Marica D. Prešić. On Free Commutative Groupoids. Publications de l'Institut Mathématique, _N_S_27 (1980) no. 41, p. 209 . http://geodesic.mathdoc.fr/item/PIM_1980_N_S_27_41_a29/