http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1826825
http://www.mitpressjournals.org/doi/abs/10.1162/DAED_a_00114
http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1826825
http://www.mitpressjournals.org/doi/abs/10.1162/DAED_a_00114