Gaya APA
Christopherson, R, W. (2014).
GEOSYSTEMS AN INTRODUCTION TO PHYSICAL GEOGRAPHY. Eigth Edition .
:
Pearson New International Edition.
Gaya MLA
Christopherson, Robert, W..
"GEOSYSTEMS AN INTRODUCTION TO PHYSICAL GEOGRAPHY. Eigth Edition".
:
Pearson New International Edition,
2014.
Buku.