@article{GDZPPN002438364,
title = {An inverse problem of the wave equation.},
journal = {Mathematische Zeitschrift},
volume = {207},
year = {1991},
pages = {119-130},
zbl = {0697.35164},
url = {http://dml.mathdoc.fr/item/GDZPPN002438364}
}
Sjöstrand, J.; Ramm, A.G. An inverse problem of the wave equation.. Mathematische Zeitschrift, Tome 207 (1991) pp. 119-130. http://gdmltest.u-ga.fr/item/GDZPPN002438364/