Gelykteken: Verskil tussen weergawes

*{{Cite book | author=Cajori, Florian| authorlink = Florian Cajori| title=A History of Mathematical Notations | location=New York | publisher=Dover (reprint) | year=1993 | isbn=0-486-67766-4}}

* Boyer, C. B.: ''A History of Mathematics'', 2nd ed. rev. by [[Uta Merzbach|Uta C. Merzbach]]. New York: Wiley, 1989 {{ISBN|0-471-09763-2}} (1991 pbk ed. {{ISBN|0-471-54397-7}})