@article{SF_1977__15_134249,
     author = {B. Bir\'o and E.W. Kiss and P.P. Palfy},
     title = {On the congruence extension property.},
     journal = {Semigroup forum},
     pages = {183--184},
     publisher = {mathdoc},
     volume = {15},
     year = {1977},
     zbl = {0384.08003},
     url = {http://geodesic.mathdoc.fr/item/SF_1977__15_134249/}
}