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The River Rom , also known as the River Beam below its confluence with the Ravensbourne , is a tributary of the River Thames in England that flows through east London suburbs surrounding the metropolitan centre of Romford , forming the boundary between the London boroughs of Barking and Dagenham and Havering .
 location: London; location: Romford; location: Barking and Dagenham; location: Havering
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:
 location: London; location: Romford; location: Barking and Dagenham; location: Havering