Global three-neutrino vacuum oscillation fits to the solar and atmospheric anomalies

We determine the three-neutrino mixing and mass parameters that are allowed by the solar and atmospheric neutrino data when vacuum oscillations are responsible for both phenomena. The global fit does not appreciably change the allowed regions for the parameters obtained from effective two-neutrino fits. We discuss how measurements of the solar electron energy spectrum below 6.5 GeV in Super-Kamiokande and seasonal variations in the Super-Kamiokande, ${}^{71}\mathrm{Ga}$, and BOREXINO experiments can distinguish the different solar vacuum solutions.