  Leptogenesis induced by the oscillations of GeV-scale neutrinos provides a
minimal and testable explanation of the baryon asymmetry of the Universe. In
this work we extend previous studies invoking only two heavy neutrinos to the
case of three heavy neutrinos. We find qualitatively new behaviour as a result
of lepton number violating oscillations and decays, strong flavour effects in
the washout and a resonant enhancement due to matter effects. An approximate
global $B - \bar L$ symmetry (representing the difference of baryon and a
generalised lepton number) can protect the light neutrino masses from large
radiative corrections, while simultaneously providing the ingredients for the
resonant enhancement of the lepton asymmetry due to thermal contributions to
the heavy neutrino dispersion relations. This mechanism is particularly
efficient for large heavy neutrino mixing angles near the current experimental
limits, a regime in which leptogenesis is not feasible in the minimal scenario
with two heavy neutrinos. In this new parameter regime, low-scale leptogenesis
is testable by the LHC and other existing experiments.
