“quartum”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
“quartum”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
quartum 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)
quartum in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.