Gaya APA
Lehmann, A, D. (1980).
Travel and tourism : an introduction to travel agency operations (1st ed.).
Indianapolis:
Bobbs-Merrill.
Gaya MLA
Lehmann, Armin, D..
"Travel and tourism : an introduction to travel agency operations".
1st ed.
Indianapolis:
Bobbs-Merrill,
1980.
BUKU.