@article{UZERU_2007_1_a4,
     author = {S. R. Aleksanyan},
     title = {On proof normal forms for some systems of classical propositional logic},
     journal = {Proceedings of the Yerevan State University. Physical and mathematical sciences},
     pages = {39--45},
     year = {2007},
     number = {1},
     language = {hy},
     url = {http://geodesic.mathdoc.fr/item/UZERU_2007_1_a4/}
}