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From 1921 , Belfast and Derry were part of Northern Ireland and stayed within the United Kingdom on the establishment of the Irish Free State in 1922 .
 Belfast, Derry, Northern Ireland, United Kingdom, Irish Free State
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Belfast, Derry, Northern Ireland, United Kingdom, Irish Free State