@article{IM2_1969_3_1_a2,
     author = {V. A. Yankov},
     title = {Conjunctively indecomposable formulas in propositional calculi},
     journal = {Izvestiya. Mathematics },
     pages = {17--35},
     publisher = {mathdoc},
     volume = {3},
     number = {1},
     year = {1969},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1969_3_1_a2/}
}