Kunitzsch 2003, p. 7: "Les personnes qui se sont occupées de la science du calcul n'ont pas été d'accord sur une partie des formes de ces neuf signes; mais la plupart d'entre elles sont convenues de les former comme il suit." Kunitzsch, Paul (2003). "The Transmission of Hindu–Arabic Numerals Reconsidered". In J. P. Hogendijk; A. I. Sabra (eds.). The Enterprise of Science in Islam: New Perspectives. MIT Press. pp. 3–22. ISBN978-0-262-19482-2.
Kunitzsch 2003, pp. 12–13: "While specimens of Western Arabic numerals from the early period—the tenth to thirteenth centuries—are still not available, we know at least that Hindu reckoning (called ḥisāb al-ghubār) was known in the West from the 10th century onward..." Kunitzsch, Paul (2003). "The Transmission of Hindu–Arabic Numerals Reconsidered". In J. P. Hogendijk; A. I. Sabra (eds.). The Enterprise of Science in Islam: New Perspectives. MIT Press. pp. 3–22. ISBN978-0-262-19482-2.
Uy, Frederick L. (January 2003). "The Chinese Numeration System and Place Value". Teaching Children Mathematics. 9 (5): 243–247. doi:10.5951/tcm.9.5.0243. ISSN1073-5836.
Danna, Raffaele; Iori, Martina; Mina, Andrea (22 June 2022). "A Numerical Revolution: The Diffusion of Practical Mathematics and the Growth of Pre-modern European Economies". SSRN4143442.
Uy, Frederick L. (January 2003). "The Chinese Numeration System and Place Value". Teaching Children Mathematics. 9 (5): 243–247. doi:10.5951/tcm.9.5.0243. ISSN1073-5836.