62553
In addition to the Swets definitions , four relevance metrics have also been defined : Precision refers to the fraction of relevant documents that are retrieved ( a / ( a + b ) ) , and Recall refers to the fraction of retrieved documents that are relevant ( a / ( a + c ) ) .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 None