@article{IM2_1985_25_1_a4,
     author = {G. S. Makanin},
     title = {Decidability of the universal and positive theories of a~free group},
     journal = {Izvestiya. Mathematics },
     pages = {75--88},
     publisher = {mathdoc},
     volume = {25},
     number = {1},
     year = {1985},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1985_25_1_a4/}
}