  We present a derivation of the flavor neutrino states which describe
neutrinos produced or detected in charged-current weak-interaction processes,
including those operating in neutrino oscillation experiments. We also present
a covariant derivation of the probability of neutrino oscillations which is
consistent with the fact that flavor is Lorentz-invariant. Finally, we clarify
the negative answers to three commonly asked questions: "Do charged leptons
oscillate?"; "Is the standard phase wrong by a factor of 2?" "Are flavor
neutrinos described by Fock states?".
