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Bredt also discovered that a double bond can not be placed at the bridgehead of a bridged ring system , a statement now known as Bredt 's rule .
 Bredt, Bredt
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Bredt, Bredt