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Leibniz produced an equation for planetary orbits in which the centrifugal force appeared as an outward inverse cube law force in the radial direction : Newton himself appears to have previously supported an approach similar to that of Leibniz .
 Leibniz, Newton, Leibniz
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Leibniz, Newton, Leibniz