@article{10_4064_cm_21_2_169_177,
     author = {J. Dudek},
     title = {Number of algebraic operations in idempotent groupoids},
     journal = {Colloquium Mathematicum},
     pages = {169--177},
     publisher = {mathdoc},
     volume = {21},
     number = {2},
     year = {1970},
     doi = {10.4064/cm-21-2-169-177},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-21-2-169-177/}
}