@article{AL_1968_7_2_a1,
     author = {V. M. Kopytov and I. I. Mamaev},
     title = {Absolute convexity of certain subgroups of an orderable group},
     journal = {Algebra i logika},
     pages = {20--26},
     publisher = {mathdoc},
     volume = {7},
     number = {2},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1968_7_2_a1/}
}