Fleenor, Charles R. Investigating school mathematics [electronic resource] / [by] Charles R. Fleenor, Robert E. Eicholz [and] Phares O'Daffer. Consulting authors: Merrill E. Shanks [and] Charles F. Brumfiel.. — Menlo Park, Calif., : Addison-Wesley Pub. Co., [1974]. — 1 v. (various pagings) : illus. 25 cm.