Gaya APA
Geosystems. (2000).
New York:
Prentice-Hall.
Gaya Chicago
Geosystems.
Fourth Edition.
New York:
Prentice-Hall,
2000.
.
Gaya MLA
Geosystems.
Fourth Edition.
New York:
Prentice-Hall,
2000.
.
Gaya Turabian
Geosystems.
New York:
Prentice-Hall,
2000.
.