@article{AL_2014_53_5_a3,
     author = {D. O. Ptakhov},
     title = {Primitive normality and additivity of free projective and strongly flat polygons},
     journal = {Algebra i logika},
     pages = {614--624},
     year = {2014},
     volume = {53},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_2014_53_5_a3/}
}