@article{DAN_1986_288_1_a0,
     author = {V. A. Vardanyan},
     title = {Arithmetic complexity of provability predicate logics and their},
     journal = {Doklady Akademii Nauk},
     pages = {11--14},
     publisher = {mathdoc},
     volume = {288},
     number = {1},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1986_288_1_a0/}
}