@article{DAN_1989_307_2_a7,
     author = {I. M. Spitkovsky and A. M. Tashbaev},
     title = {Factorization of piecewise constant matrix functions with $3$},
     journal = {Doklady Akademii Nauk},
     pages = {291--296},
     publisher = {mathdoc},
     volume = {307},
     number = {2},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1989_307_2_a7/}
}