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The absence of the author 's final revision may explain many errors , and as early as 1350 , Petrarch complained about the corrupt state of the text , referring to copying errors made between the ninth and eleventh centuries .
 Petrarch
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Petrarch