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Jeffrey S. Medkeff ( 1968 – 3 August 2008 ) , usually known as Jeff Medkeff , was a prominent science writer and educator .
 Jeffrey S. Medkeff, Medkeff
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Jeffrey S. Medkeff, Medkeff