Gaya APA
Valkenburg, S, &, C. (1960).
Elements of political geography, 2md ed. Cet.pertama 1954. .
Englewood Cliffs:
NJ Prentice-Hall.
Gaya MLA
Valkenburg, S.van, &, C.L.Stotz..
"Elements of political geography, 2md ed. Cet.pertama 1954. ".
Englewood Cliffs:
NJ Prentice-Hall,
1960.
Buku.