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Antimatter production is currently very limited , but has been growing at a nearly geometric rate since the observation of the first antiproton in 1955 by Segrè and Chamberlain .
 Segrè, Chamberlain
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Segrè, Chamberlain