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It was formed from the nationalisation of the " Big Four " British railway companies and lasted until the gradual privatisation of British Rail , in stages between 1994 and 1997 .
 organization: Big Four; organization: British Rail
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 organization: Big Four; organization: British Rail