【邮箱】http://econpapers.repec.org/article/oupoxford/v_3a12_3ay_3a1996_3ai_3a4_3ap_3a27-52.htm

http://www.jstor.org/discover/10.2307/23606400?uid=3737800&uid=2&uid=4&sid=21106475484753

http://oxrep.oxfordjournals.org/content/12/4/27.short