@article{MZM_1980_28_4_a4,
     author = {S. P. Belinskii and V. G. Romanov},
     title = {Determination of the coefficients of a $t$-hyperbolic system},
     journal = {Matemati\v{c}eskie zametki},
     pages = {525--532},
     publisher = {mathdoc},
     volume = {28},
     number = {4},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1980_28_4_a4/}
}