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A somewhat similar approach was taken by Robert A. Heinlein in his 1941 novelette " Elsewhen " , in which a professor trains his mind to move his body across timelines .
 Robert A. Heinlein
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Robert A. Heinlein