@article{PORMA_1975__34_3_115261,
     author = {Rosenberg, I.G.},
     title = {Special types of universal algebras preserving a relation},
     journal = {Portugaliae mathematica},
     pages = {173--188},
     publisher = {mathdoc},
     volume = {34},
     number = {3},
     year = {1975},
     mrnumber = {0465992},
     zbl = {0327.08008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1975__34_3_115261/}
}