@article{702357,
     title = {On regularity of solutions to some problems of mathematical physics},
     booktitle = {Equadiff 7},
     series = {GDML\_Books},
     publisher = {BSB B.G. Teubner Verlagsgesellschaft},
     address = {Leipzig},
     year = {1990},
     pages = {180-182},
     zbl = {0785.35026},
     url = {http://dml.mathdoc.fr/item/702357}
}

Koshelev, A. I.; Chelkak, S. I.; Chistyakov, V. M. On regularity of solutions to some problems of mathematical physics, dans Equadiff 7, GDML_Books,  (1990), pp. 180-182. http://gdmltest.u-ga.fr/item/702357/