@article{AL_1991_30_4_a1,
     author = {R. Sh. Omanadze},
     title = {On the upper semilattice of recursively enumerable ${\rm},
     journal = {Algebra i logika},
     pages = {405--413},
     publisher = {mathdoc},
     volume = {30},
     number = {4},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1991_30_4_a1/}
}