Note 905 — Chapter XIII · THE FORM-WORLD OF ECONOMIC LIFE (A) MONEY
Charles Francis Atkinson translation
Hampe, Deutsche Kaisergeschichte, p. 246. Leonardo Pisano, whose Liber Abaci (1202) was authoritative in accountancy till well beyond the Renaissance, and who introduced, besides the Arabian system of numerals, negative numbers to indicate debit, was promoted by the great Hohenstaufen.