@article{AL_1978_17_6_a2,
     author = {S. D. Denisov},
     title = {Structure of the upper semilattice of recursively enumerable},
     journal = {Algebra i logika},
     pages = {643--683},
     year = {1978},
     volume = {17},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1978_17_6_a2/}
}