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The term " speciesism " , and the argument that it is a prejudice , first appeared in 1970 in a privately printed pamphlet written by British psychologist Richard D. Ryder .
 Richard D. Ryder
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Richard D. Ryder