Recorde is known for introducing the "equal to" sign, i.e. "=". He published several mathematical works, including The Grounde of Artes, teachings the Worke and Practise, of Arithmeticke, both in whole numbers and fractions in 1543, which was the first book on Algebra published in England, and The Whetstone of Witte, whiche is the seconde parte of Arithmeteke: containing the extraction of rootes; the cossike practise, with the rule of equation; and the workes of Surde Nombers, in which he introduced the "=" sign.