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The general idea of natural equations for obtaining curves from local curvature appears to have been first considered by Leonhard Euler in 1736 , and many examples with fairly simple behavior were studied in the 1800 s .
 person: Leonhard Euler
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 person: Leonhard Euler