@article{MZM_1995_57_4_a11,
     author = {R. S. Khairullin},
     title = {Tricomi's problem for a~second order system of equations},
     journal = {Matemati\v{c}eskie zametki},
     pages = {625--632},
     publisher = {mathdoc},
     volume = {57},
     number = {4},
     year = {1995},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1995_57_4_a11/}
}