16673
Further experimentation by Rutherford found that the nuclear mass of most atoms exceeded that of the protons it possessed ; he speculated that this surplus mass was composed of previously-unknown neutrally charged particles , which were tentatively dubbed " neutrons " .
 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