Cita APA (7th ed.)
(1991). The World book health and medical annual 1991. World book.
Cita Chicago (17th ed.)
The World Book Health and Medical Annual 1991. Chicago: World book, 1991.
Cita MLA (9th ed.)
The World Book Health and Medical Annual 1991. World book, 1991.
Atenció: Aquestes cites poden no estar 100% correctes.