The term "Late Middle Ages" refers to one of the three periods of the Middle Ages, along with the Early Middle Ages and the High Middle Ages. Leonardo Bruni was the first historian to use tripartite periodization in his History of the Florentine People (1442). Flavio Biondo used a similar framework in Decades of History from the Deterioration of the Roman Empire (1439–1453). Tripartite periodization became standard after the German historian Christoph Cellarius published Universal History Divided into an Ancient, Medieval, and New Period (1683).
Try to answer this question if possible (otherwise reply "unanswerable"): What isn't the name for the division of the periods of history introduced by Bruni?
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