Brown, Tim
Wiley Blackwell, 2010
Buku Teks SO
Andrews, Gavin J., 1970-
Routledge, Taylor & Francis Group, 2018
Buku Teks SO
edited by Pavlos Kanaroglou, Eric Delmelle and Antonio Páez
Routledge, 2018
Buku Teks SO
Taylor and Francis, 2018
Buku Teks SO
edited by Alastair Gray
Open University Press, 2001
Buku Teks SO