APA (7th ed.) Citation

(1999). Guinness book of the 20th century (Millennium Edition.). Guinness World Records.

Chicago Style (17th ed.) Citation

Guinness Book of the 20th Century. Millennium Edition. London: Guinness World Records, 1999.

MLA (8th ed.) Citation

Guinness Book of the 20th Century. Millennium Edition. Guinness World Records, 1999.

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