UNDERHILL, R. G. (1977). Teaching elementary school mathematics.-- ed.2. Charles E.Merill pub.
Cita Chicago (17th ed.)UNDERHILL, Robert G. Teaching Elementary School Mathematics.-- Ed.2. Columbus: Charles E.Merill pub, 1977.
Cita MLA (9th ed.)UNDERHILL, Robert G. Teaching Elementary School Mathematics.-- Ed.2. Charles E.Merill pub, 1977.
Atenció: Aquestes cites poden no estar 100% correctes.