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@article{MOMA_1992__113_4_178552, author = {Markku Niemenmaa and Tomas Kepka}, title = {On a {General} {Associativity} {Law} in {Groupoids.}}, journal = {Monatshefte f\"ur Mathematik}, pages = {51--58}, publisher = {mathdoc}, volume = {113}, number = {4}, year = {1992}, zbl = {0768.20032}, url = {http://geodesic.mathdoc.fr/item/MOMA_1992__113_4_178552/} }
Markku Niemenmaa; Tomas Kepka. On a General Associativity Law in Groupoids.. Monatshefte für Mathematik, Tome 113 (1992) no. 4, pp. 51-58. http://geodesic.mathdoc.fr/item/MOMA_1992__113_4_178552/