(Lib'-nitz, 1646-1716). Photographs of these three men with brief notes about them occur in this book.

As to the symbols +, =, etc., these came into use only after the invention of printing, being introduced as convenient abbreviations. For example, the signs and first occur in a German text published in 1489, while the sign = was first used by the English physician Robert Recorde, (1510-1558), who published the first English work on algebra, calling it the "Whetstone of Witte" (whetstone of wit).

Detailed accounts of the origin and development of algebra may be found in histories of mathematics, e.g. BALL, A Short History of Mathematics; CAJORI, History of Elementary Mathematics; etc.