@article{JRAM_1965__218_150677,
     author = {R.P. Gilbert and H.C. Howard},
     title = {On solutions of the generalized bi-axially symmetric {Helmholtz} equation generated by integral operators.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {109--120},
     publisher = {mathdoc},
     volume = {218},
     year = {1965},
     zbl = {0135.32003},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1965__218_150677/}
}