@article{EmpiricalHardness,
 author = {Leyton-Brown, Kevin and Nudelman, Eugene and Shoham, Yoav},
 title = {Empirical hardness models: Methodology and a case study on combinatorial auctions},
 journal = {Journal of the ACM},
 volume = {56},
 number = {4},
 year = {2009},
 issn = {0004-5411},
 pages = {1--52},
 doi = {http://doi.acm.org/10.1145/1538902.1538906},
 publisher = {ACM},
 address = {New York, NY, USA},
}