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Robert Steven Ferrell ( born November 13 , 1952 in Los Angeles , California ) is a former professional American football running back who played for five seasons for the San Francisco 49ers of the National Football League .
 Ferrell, Los Angeles, California, San Francisco 49ers, National Football League
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Ferrell, Los Angeles, California, San Francisco 49ers, National Football League