Yoram Bachrach Evangelos Markakis Ariel D. Procaccia Jeffrey S. Rosenschein Amin Saberi Approximating power indices. 943-950 2008 AAMAS (2) http://doi.acm.org/10.1145/1402298.1402354 conf/atal/2008-2 db/conf/atal/aamas2008-2.html#BachrachMPRS08