@techreport{oai:repository.dl.itc.u-tokyo.ac.jp:00042035,
 author = {Fujiwara-Greve, Takako and Okuno-Fujiwara, Masahiro and Suzuki, Nobue},
 month = {Mar},
 note = {application/pdf, 本文フィルはリンク先を参照のこと},
 title = {Voluntarily Separable Prisoner's Dilemma with Reference Letters},
 year = {2008}
}