Cita APA (7a ed.)

Burton, S. (1990). Writing letters (1a ed.). Longman Group Uk Limited.

Cita Chicago Style (17a ed.)

Burton, S.H. Writing Letters. 1a ed. Inglaterra: Longman Group Uk Limited, 1990.

Cita MLA (9a ed.)

Burton, S.H. Writing Letters. 1a ed. Longman Group Uk Limited, 1990.