@article{MZ_1966__92_170534,
     author = {Alfred L. Foster and Alden Pixley},
     title = {Algebraic and {Equational} {Semi-Maximality;} {Equational} {Spectra:} {I.}},
     journal = {Mathematische Zeitschrift},
     pages = {30--50},
     publisher = {mathdoc},
     volume = {92},
     year = {1966},
     zbl = {0136.26101},
     url = {http://geodesic.mathdoc.fr/item/MZ_1966__92_170534/}
}