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Samuel Barber , Sergei Rachmaninoff , Roger Quilter , Howard Skempton , John Vanderslice , and Ralph Vaughan Williams composed music based on his poems .
 Samuel Barber, Sergei Rachmaninoff, Roger Quilter, Howard Skempton, John Vanderslice, Ralph Vaughan Williams
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Samuel Barber, Sergei Rachmaninoff, Roger Quilter, Howard Skempton, John Vanderslice, Ralph Vaughan Williams