219900
The Revival was marked by a series of major concerts in the United States , and also spread to Europe where events such as the Wembley concert attracted thousands of fans who came out to see the performers behind the music .
 United States, Europe
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 United States, Europe