1477
An inverse cube law centrifugal force appears in an equation representing planetary orbit s , including non-circular ones , as Leibniz described in his 1689 Tentamen de motuum coelestium causis .
 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