@article{01923111,
title = {On two boundary value problems for mixed type equations with perpendicular lines of type change.},
journal = {Vladikavkazski\u\i\ Matematicheski\u\i\ Zhurnal},
volume = {3},
year = {2001},
pages = {9-22},
zbl = {1022.35029},
language = {en},
url = {http://dml.mathdoc.fr/item/01923111}
}
Eleev, V.A.; Lesev, V.N. On two boundary value problems for mixed type equations with perpendicular lines of type change.. Vladikavkazskiĭ Matematicheskiĭ Zhurnal, Tome 3 (2001) pp. 9-22. http://gdmltest.u-ga.fr/item/01923111/