Irma Taavitsainen, Paivi Pahta, editor
Cambridge University Press, 2011
Buku Teks
edited by Paul Poplawski
Cambridge University Press, 2017
Buku Teks
Haley, Elie, author
Pelican Book, 1937
Buku Referensi
Mike Fitzgerald, Gregor McLennan and Jennie Pawson at the Open University.
Routledge in association with Open University Press, 2001
Buku Teks
Robbins, Lionel Robbins, Baron, 1898-1984, editor
McMillan & Co., 1952
Buku Teks