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The " labarum " was a " vexillum " ( military standard ) that displayed the " Chi-Rho " symbol , a christogram formed from the first two Greek letters of the word " Christ " ( , or Χριστός ) - " Chi " ( χ ) and " Rho " ( ρ ) .
 Christ, Rho
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Christ, Rho