APA (7th ed.) Citation

(1990). When it happened: A question-and-answer book about world history. Kingfisher Books.

Chicago Style (17th ed.) Citation

When It Happened: A Question-and-answer Book About World History. London: Kingfisher Books, 1990.

MLA (9th ed.) Citation

When It Happened: A Question-and-answer Book About World History. Kingfisher Books, 1990.

Warning: These citations may not always be 100% accurate.