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In the latter half of the 1800 s , several inventors worked towards creating a method for doing just that , including Charles Bourseul , Thomas Edison , Elisha Gray , and Alexander Graham Bell .
 Charles Bourseul, Thomas Edison, Elisha Gray, Alexander Graham Bell
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Charles Bourseul, Thomas Edison, Elisha Gray, Alexander Graham Bell