Nikolaj Bittner, Dietrich Einzel, Ludwig Klam, and Dirk Manske: Leggett Modes and the Anderson-Higgs Mechanism in Superconductors without Inversion
            Symmetry. 2015Phys. Rev. Lett.: 115. http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.227002