Chen, Po and Jordan, Thomas H. and Zhao, Li  (2010) Resolving fault plane ambiguity for small earthquakes.  Geophysical Journal International, 181 (1).  pp. 493-501. DOI: https://doi.org/10.1111/j.1365-246X.2010.04515.x <https://doi.org/10.1111/j.1365-246X.2010.04515.x>