Egger, P., and M. Pfaffermayr (2004). Distance, Trade, and FDI: A Hausman-Taylor SUR Approach. Journal of Applied Econometrics 19(2), 227-246, http://qed.econ.queensu.ca/jae/2004-v19.2/egger-pfaffermayr/
Mayer, T., and S. Zignago (2011). Notes on CEPII's distances measures: The GeoDist Database. CEPII Working Paper 2011-25, http://www.cepii.fr/CEPII/en/publications/wp/abstract.asp?NoDoc=3877