@article{AL_2021_60_6_a4,
     author = {N. T. Kogabaev},
     title = {Complexity of the problem of being equivalent to {Horn} formulas},
     journal = {Algebra i logika},
     pages = {575--586},
     year = {2021},
     volume = {60},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_2021_60_6_a4/}
}