“The Greek mathematician Diophantus of Alexandria... it seems fairly probable... flourished about 250 A.D. ...We gather from the Arithmeticas introduction that it originally consisted of thirteen Books. Of these, only six have survived until now in Greek... The remaining seven were considered irretrievably lost until the recent discovery of four other, hitherto unknown books in Arabic translation, which, since it is attributed to Qustā ibn Lūqā, must have been made around or after the middle of the ninth century.”