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In 1905 , Albert Einstein theorized that this Brownian motion was caused by the water molecules continuously knocking the grains about , and developed a hypothetical mathematical model to describe it .
 Albert Einstein, Brownian
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Albert Einstein, Brownian