Complex sentence: These approaches have built on the Ricardian formulation of two goods for two countries and elaborated models accounting for multiple goods and multiple countries in order to reflect real-world conditions more accurately.
Split into simpler sentences: These approaches have built on the Ricardian formulation of two goods for two countries and subsequent models with many goods or many countries. The aim have been to reach a formulation accounting for boty multiple goods and multiple countries, in order to reflect real-world conditions more accurately.