From Citizendium, the Citizens' Compendium
- Please sort and annotate in a user-friendly manner. For formatting, consider using automated reference wikification.
- Conant, Levi Leonard. The Number Concept: Its Origin and Development (1896), 218 pp. online edition
- Sarton, George. "Decimal Systems Early and Late," Osiris, Vol. 9. (1950), pp. 581-601. in JSTOR
- Smith, David Eugene, and Louis Charles Karpinski. The Hindu-Arabic Numerals, (1911) 160pp online edition