@article{VMUMM_1984_2_a6,
     author = {V. N. Krivtsov},
     title = {A type of formal negationless systems},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {27--31},
     publisher = {mathdoc},
     number = {2},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1984_2_a6/}
}