2Yang X. Endogenous vs. exogenous comparative advantage and economies of specialization vs. economies of scale [J]. Journal of Economics, 1994(60) .29 -54.
3Cheng W, Sachs J, Yang X. An Infra - marginal analysis of the ricardian model [ J ]. Review of International Economics, 2000 ( 8 ) : 208 - 220.
4Cheng W, Liu M, Yang X. A ricardian model with endogenous comparative advantage and endogenous trade policy regimes [ J], The Economic Record, 2000 (76) : 172 - 183.