APA (7th ed.) Citation

(1966). The New Book of Knowledge, Volume 21 Index. Grolier.

Chicago Style (17th ed.) Citation

The New Book of Knowledge, Volume 21 Index. Grolier, 1966.

MLA (8th ed.) Citation

The New Book of Knowledge, Volume 21 Index. Grolier, 1966.

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