@book{Murphy_2012, address={Cambridge}, edition={4th ed}, title={English grammar in use with answers: a self-study reference and practice book for intermediate learners of English}, publisher={Cambridge University Press}, author={Murphy, Raymond}, year={2012} }
@book{Swan_2005, address={Oxford}, edition={3rd ed}, title={Practical English usage}, publisher={Oxford University Press}, author={Swan, Michael}, year={2005} }