It is true because if you look for colonial time books it tells you
During which time? This is not made clear
In April 1954 diplomats from several nations – including the United States, the Soviet Union, China, France and Great Britain – attended a conference in Geneva, Switzerland. The Geneva gathering was convened to discuss two Cold War hotspots, Berlin and Korea – but by the time it began the Viet Minh<span> had overrun the French base at </span>Dien Bien Phu<span>, forcing Vietnam onto the agenda. By the start of May, Paris had announced its intention to withdraw from Indochina and dismantle the </span>colonial administration<span> there. The French withdrawal would leave Vietnam without an established national government, placing it at risk of a communist takeover. The Geneva conference was given the unenviable task of arranging for Vietnam’s reunification and self government. The conference produced a set of resolutions known as the Geneva Accords, a road map for Vietnam’s transition to independence. The Accords were not supported by major players, however, so had little chance of success.</span>
You get a greater gain from trade when the trading partners produce goods for which they each have comparative advantage.
