@article{FPM_2000_6_1_a4,
     author = {D. A. Bredikhin},
     title = {$\mathbf U$-semigroups of relations},
     journal = {Fundamentalʹna\^a i prikladna\^a matematika},
     pages = {51--61},
     publisher = {mathdoc},
     volume = {6},
     number = {1},
     year = {2000},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FPM_2000_6_1_a4/}
}