  We show that quantum-interference-related phenomena, such as
electromagnetically induced transparency, gain without inversion and enhanced
refractive index may occur on electric-dipole forbidden transitions.
Gain/dispersion characteristics of such transitions strongly depend upon the
relative phase between the driving and probe fields. Unlike allowed
transitions, gain/absorption behavior of forbidden transitions exhibit
antisymmetric feature on the Rabi sidebands. Absorption/gain spectra possess
extremely narrow sub-natural resonances.
