77769
He sketched a program for proving the consistency of Zermelo–Fraenkel set theory using ultrafinitistic techniques in , and .
 Zermelo–Fraenkel
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Zermelo–Fraenkel