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His theory is based on three axioms : ( 1 ) the principle of relativity , ( 2 ) a generalized Mach principle , in which electromagnetism and gravity , as well as inertial mass , derives from the interaction of matter , and ( 3 ) a correspondence principle .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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