510.7 Bru D Brueckner, Leo John, 1890- Developing mathematical understandings in the upper grades [by] Leo J. Brueckner, Fosti E. Grossnickle [and] John Reckzeh. Philadephia,J. C. Winston [cl957] 567 p. ilus., diagrs., tablas. 22 cm BibliografĂ­a al final de los capĂ­tulos.