8Becerril J, Abdulai A. The impact of improved maize varieties on poverty in Mexico: A propensity score matc- hing approach [ J ]. World Development, 2009,38 (7) : 1024 - 1035.
9Park J, Mcfarlance I, Phipps R. The impact of the EU regulatory constraint of transgenic crops on farm income [ J ]. New Sioteehnology,2011,28 (4) : 396 - 406.
10Hayami Y, Herdt R W. Market price effects of technological change on income distribution in semi subsistence agriculture [ J ]. American Journal of Agricultural Economics, 1997,59 (2) :245 - 256.