78638
Banach spaces originally grew out of the study of function spaces by Hilbert , Fréchet , and Riesz earlier in the century .
 Hilbert, Fréchet, Riesz
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Hilbert, Fréchet, Riesz