Matter-wave dark solitons and their excitation spectra in spin-orbit coupled Bose-Einstein condensatesV. Achilleos, J. Stockhofe, P. G. Kevrekidis, D. J. Frantzeskakis and P. SchmelcherEPL, 103 2 (2013) 20002DOI: https://doi.org/10.1209/0295-5075/103/20002