What are the four theorems of international trade?

H-O Theorem: The relative factor abundance or factor endowment of each country is the basic reason and decisive factor for the comparative advantage of each country in international trade. Some people say that we should produce and export the relatively abundant and cheap factor-intensive goods in this country and import the scarce and expensive factor-intensive goods in this country.

FE Theorem: International trade means that the relative income and absolute income of homogeneous factors in all countries are the same, that is, under the same conditions, international trade will eventually lead to the equalization of relative and absolute prices of production factors in all countries, and international trade will replace the international factor flow to some extent.

S-S Theorem: If the relative price of a commodity increases, it will increase the price of the factors of production intensively used by the commodity and reduce the prices of the factors of production intensively used by other commodities. (i.e. long-term effects)

R Theorem: Under the condition that the relative price of commodities remains unchanged, the increase of a certain factor of production will increase the output of commodities that use this factor intensively, while the output of commodities that use other factors of production intensively will decrease.