Cita APA (7th ed.)

Hitt Espinosa, F. A., & Santos, M. (1999). Proceedings of the twenty first annual meeting: Psychology of mathematics education PME-NA XXI. ERIC.

Cita Chicago (17th ed.)

Hitt Espinosa, Fernando Antonio, i Manuel Santos. Proceedings of the Twenty First Annual Meeting: Psychology of Mathematics Education PME-NA XXI. Columbus: ERIC, 1999.

Cita MLA (9th ed.)

Hitt Espinosa, Fernando Antonio, i Manuel Santos. Proceedings of the Twenty First Annual Meeting: Psychology of Mathematics Education PME-NA XXI. ERIC, 1999.