ferramentum in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
ferramentum in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.