Gaya APA
Lopker, J.
(2000).
Pictures of Personality : guide to the four human natures
(
Ed.1)
.
Los Angeles:
Typology.
Gaya MLA
Lopker, John.
"Pictures of Personality : guide to the four human natures".
Ed.1
Los Angeles:
Typology,
2000.
Buku Tercetak.