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where " γ " is the Euler–Mascheroni constant and ζ ' is the derivative of the Riemann zeta function .
 Euler–Mascheroni, Riemann
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Euler–Mascheroni, Riemann