International Factor Price Equalization Theorem deals with the international distribution of income. Stolper-Samuelson Theorem deals with the distribution of income effects of international trade within a trading country. Heckscher-Ohlin Theory states that comparative advantage of the trading countries is explained exclusively by differences in relative supply conditions. Classical Trade Theory which has been accepted as the primer of the international trade theory assumes that the country whose labor is more productive in producing the commodity that is subject to international trade has a comparative advantage in this commodity. Briefly, the basis of international trade solely depends on the differences of labor productivity.