Gaya APA
Riso, D, R. (1990).
Understanding the enneagram: The practical guide to persona- lity types. .
Boston:
Boston Houghton Mifflin Company.
Gaya MLA
Riso, Don, Richard.
"Understanding the enneagram: The practical guide to persona- lity types. ".
Boston:
Boston Houghton Mifflin Company,
1990.
Buku.