4Jin S,Zhou J. Adoption of food safety and quality standards by China' s agricult ural cooperatives[J]. Food Control, 2011,22 (2) :204-208.
5Heckman J. Sample selection bias as a specification error[J]. Econometrica,1979,47(1) :153-161.
6Goodhue R. Broiler production contracts as a multi agent problem: Common risk, incentives and heterogeneity [J].American Journal of Agricultural Economics, 2000,82 :606-622.
7Alexander C R,Goodhue G Rausser. Do incentives for quality matter? [J]. Journal of Agricultural and Applied Economics, 2007,39(1) :1-15.