APA (7th ed.) Citation

Shiu, C. M., & Bell, A. W. (1981). Directed number. Shell Centre for Math. Education.

Chicago Style (17th ed.) Citation

Shiu, Christine M., and Alan W. Bell. Directed Number. Nottingham: Shell Centre for Math. Education, 1981.

MLA (9th ed.) Citation

Shiu, Christine M., and Alan W. Bell. Directed Number. Shell Centre for Math. Education, 1981.

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