@article{FPM_1999_5_2_a4,
     author = {V. K. Zakharov and A. V. Mikhalev},
     title = {A~two-sorted theory of classes and sets, admitting sets of propositional formulas},
     journal = {Fundamentalʹna\^a i prikladna\^a matematika},
     pages = {417--435},
     publisher = {mathdoc},
     volume = {5},
     number = {2},
     year = {1999},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FPM_1999_5_2_a4/}
}