187436
Thanks to the grant he received from the Art Institute of Photography he was able to study for a year under Harry Callahan and Aaron Siskind .
 Harry Callahan, Aaron Siskind
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Harry Callahan, Aaron Siskind