@article{AL_1973_12_2_a3,
     author = {Yu. L. Ershov and I. A. Lavrov},
     title = {The upper semilattice $L(\gamma )$},
     journal = {Algebra i logika},
     pages = {167--189},
     publisher = {mathdoc},
     volume = {12},
     number = {2},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1973_12_2_a3/}
}