@article{MZM_1977_22_6_a4,
     author = {V. M. Bruk},
     title = {Extensions of symmetric relations},
     journal = {Matemati\v{c}eskie zametki},
     pages = {825--834},
     publisher = {mathdoc},
     volume = {22},
     number = {6},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1977_22_6_a4/}
}