%0 Journal Article %T Separation of the Helmholtz partial differential equation in Hilbert space %A S. Omran %A Kh. A. Gepreel %J Advanced Studies in Theoretical Physics %D 2012 %I %U http://www.m-hikari.com/astp/astp2012/astp9-12-2012/gepreelASTP9-12-2012.pdf