@article{GDZPPN002205408,
title = {A class of boundary problems for extremal surfaces of mixed type in Minkowski 3-space.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {390},
year = {1988},
pages = {195-202},
zbl = {0635.49019},
url = {http://dml.mathdoc.fr/item/GDZPPN002205408}
}
Gu, Chaohao. A class of boundary problems for extremal surfaces of mixed type in Minkowski 3-space.. Journal für die reine und angewandte Mathematik, Tome 390 (1988) pp. 195-202. http://gdmltest.u-ga.fr/item/GDZPPN002205408/