54573
In 1913 , Ernst Zermelo used chess as a basis for his theory of game strategies , which is considered as one of the predecessors of game theory .
 Ernst Zermelo
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:
 Ernst Zermelo