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During World War I , Eddington was Secretary of the Royal Astronomical Society , which meant he was the first to receive a series of letters and papers from Willem de Sitter regarding Einstein 's theory of general relativity .
 person: Eddington; organization: Royal Astronomical Society; person: Willem de Sitter; person: Einstein
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 person: Eddington; organization: Royal Astronomical Society; person: Willem de Sitter; person: Einstein