@article{AL_1970_9_6_a10,
     author = {D. J. Collins},
     title = {A universal semigroup},
     journal = {Algebra i logika},
     pages = {731--740},
     publisher = {mathdoc},
     volume = {9},
     number = {6},
     year = {1970},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AL_1970_9_6_a10/}
}