@article{TRSPY_1988_182_a7,
     author = {P. L. Ul'yanov},
     title = {Metric function theory},
     journal = {Informatics and Automation},
     pages = {180--223},
     publisher = {mathdoc},
     volume = {182},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TRSPY_1988_182_a7/}
}