371071
Ruffin , up to this point , had only sung lead on stage and on a few unreleased tracks , otherwise singing backgrounds behind Kendricks and then main lead singer Paul Williams .
 Ruffin, Kendricks, Paul Williams
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Ruffin, Kendricks, Paul Williams