@article{AL_1968_7_5_a3,
     author = {Ahmad Shafaat},
     title = {Clusters of algebra},
     journal = {Algebra i logika},
     pages = {109--116},
     publisher = {mathdoc},
     volume = {7},
     number = {5},
     year = {1968},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AL_1968_7_5_a3/}
}