Al-Khwarizmi - Biography(англ.). Maths History. — «only the first part of the book is a discussion of what we would today recognise as algebra». Дата обращения: 2 июля 2024.
Al-Khwarizmi - Biography(англ.). Maths History. — «When I consider what people generally want in calculating, I found that it always is a number. I also observed that every number is composed of units, and that any number may be divided into units. Moreover, I found that every number which may be expressed from one to ten, surpasses the preceding by one unit: afterwards the ten is doubled or tripled just as before the units were: thus arise twenty, thirty, etc. until a hundred: then the hundred is doubled and tripled in the same manner as the units and the tens, up to a thousand; ... so forth to the utmost limit of numeration.» Дата обращения: 2 июля 2024.
