@article{VMUMM_2017_3_a9,
     author = {Ya. I. Petrukhin},
     title = {Natural deduction system for three-valued {Heyting's} logic},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {63--66},
     publisher = {mathdoc},
     number = {3},
     year = {2017},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_2017_3_a9/}
}