@article{urn:eudml:doc:43823, title = {Reflection principles for the iterated Helmholtz equation.}, journal = {Collectanea Mathematica}, volume = {26}, year = {1975}, pages = {253-266}, zbl = {0333.35023}, language = {en}, url = {http://dml.mathdoc.fr/item/urn:eudml:doc:43823} }
Díaz, J. B. Reflection principles for the iterated Helmholtz equation.. Collectanea Mathematica, Tome 26 (1975) pp. 253-266. http://gdmltest.u-ga.fr/item/urn:eudml:doc:43823/