 Cohen made a number of other contributions to the field of migration studies by giving new understandings to key contested concepts such as diaspora and borders, citizens and denizens, and collective or national identity.In "Frontiers of identity", (1994) he argued that 'fuzzy' frontiers within the UK and between Britain, the Commonwealth, and the wider world create a particular ambiguous notion of 'Britishness'.His most influential work, "Global diasporas", (1997, with subsequent editions and translations) continued his analysis of the relationship between identity and migration.