@article{VMJ_2011_13_3_a3,
     author = {V. A. Koibaev},
     title = {Closed pairs},
     journal = {Vladikavkazskij matemati\v{c}eskij \v{z}urnal},
     pages = {36--41},
     publisher = {mathdoc},
     volume = {13},
     number = {3},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMJ_2011_13_3_a3/}
}