@article{03910910, title = {Some isometrical identities in the wave equation.}, journal = {International Journal of Mathematics and Mathematical Sciences}, volume = {7}, year = {1984}, pages = {117-130}, doi = {10.1155/S0161171284000132}, zbl = {0571.35064}, language = {en}, url = {http://dml.mathdoc.fr/item/03910910} }
Saitoh, Saburou. Some isometrical identities in the wave equation.. International Journal of Mathematics and Mathematical Sciences, Tome 7 (1984) pp. 117-130. doi : 10.1155/S0161171284000132. http://gdmltest.u-ga.fr/item/03910910/