Williams, E. M., & Shuard, H. (1970). Primary mathematics today. Longmans.
Cita Chicago (17th ed.)Williams, Elizabeth M., i Hilary Shuard. Primary Mathematics Today. Harlow: Longmans, 1970.
Cita MLA (9th ed.)Williams, Elizabeth M., i Hilary Shuard. Primary Mathematics Today. Longmans, 1970.
Atenció: Aquestes cites poden no estar 100% correctes.