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The subjects designated were painter Grant Wood , contralto singer Marian Anderson , authors Mark Twain and Willa Cather , musician Louis Armstrong , architect Frank Lloyd Wright , poet Robert Frost , sculptor Alexander Calder , actress Helen Hayes and author John Steinbeck .
 Grant Wood, Marian Anderson, Mark Twain, Willa Cather, Louis Armstrong, Frank Lloyd Wright, Robert Frost, Alexander Calder, Helen Hayes, John Steinbeck
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:
 Grant Wood, Marian Anderson, Mark Twain, Willa Cather, Louis Armstrong, Frank Lloyd Wright, Robert Frost, Alexander Calder, Helen Hayes, John Steinbeck