Dubbs’ Complete mental arithmetic : a volume of carefully graded exercises adapted to the use of all schools, 660 - Chandler Collection no. 5, Volume: Archives Chandler Collection no. 5. Clarion University Archives.

Dubbs’ Complete mental arithmetic : a volume of carefully graded exercises adapted to the use of all schools, 660 - Chandler Collection no. 5, Volume: Archives Chandler Collection no. 5. Clarion University Archives. http://as-clarion.klnpa.org/repositories/2/resources/986 Accessed December 23, 2025.