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留人不住,醉解兰舟去。一棹碧涛春水路,过尽晓莺啼处。154许浑:秋日赴阙题潼关驿楼If productivity measures the efficiency of an economy, a measure of what an economic system produces is its gross national product (GNP), which is the current market value of all final goods and services that a nation produces within a particular period. |