DELL’OSSO, L., SALUSTI, E., & ZURILLI, F. (1975). Some cONsideratiollS ON the usual derivation or the Pockels (or Helmholtz) equation in steady two dimensionaI fluid dYllamics. Annals of Geophysics, 28(1), 37–43. https://doi.org/10.4401/ag-4889