@article{MZ_1964__83_170222,
     author = {Alfred L. Foster and Alden Pixley},
     title = {Semi-categorical algebras. {I.} {Semi-primal} algebras.},
     journal = {Mathematische Zeitschrift},
     pages = {147--169},
     publisher = {mathdoc},
     volume = {83},
     year = {1964},
     zbl = {0117.26001},
     url = {http://geodesic.mathdoc.fr/item/MZ_1964__83_170222/}
}