Dewey, M., Beall, J., Matthews, W. E., Mitchell, J. S., & New, G. R. (1996). Dewey decimal classification and relative index (Ed. 21.). Albany, N.Y.: Forest Press, a division of OCLC Online Computer Library Center.

Dewey, Melvil, Julianne Beall, Winton E. Matthews, Joan S. Mitchell, e Gregory R. New. Dewey Decimal Classification and Relative Index. Ed. 21. Albany, N.Y.: Forest Press, a division of OCLC Online Computer Library Center, 1996.

Dewey, Melvil, et al. Dewey Decimal Classification and Relative Index. Ed. 21. Albany, N.Y.: Forest Press, a division of OCLC Online Computer Library Center, 1996.