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In 1917 Rutherford bombarded nitrogen gas with alpha particles and observed hydrogen nuclei being emitted from the gas ( Rutherford recognized these , because he had previously obtained them bombarding hydrogen with alpha particles , and observing hydrogen nuclei in the products ) .
 Rutherford, Rutherford
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Rutherford, Rutherford