@article{TM_2013_283_a7,
     author = {V. A. Il'in and A. A. Kuleshov},
     title = {Necessary and sufficient conditions for a~generalized solution to the initial-boundary value problem for the wave equation to belong to $W^1_p$ with~$p\geq1$},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {115--120},
     publisher = {mathdoc},
     volume = {283},
     year = {2013},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_2013_283_a7/}
}