Rix Helmut. The Latin Imperfect in -bā-, the Proto-Indo-European root *bhweh2- and full grade I forms from seṭ-roots with full grade II

Language in Time and Space. A Festschrift for Werner Winter on the Occasion of his 80th Birthday. — Ed. by Brigitte L.M. Bauer and Georges-Jean Pinault. — Berlin; New York: de Gruyter, 2003. — P. 363–384.Latin imperfect in -bā- was formed on the model of Proto-Italic *fuβ(w)ām, *fuβ(w)ās, *fuβ(w)ād (Osc. fufans, etc.) which itself was a pluperfect of the the root 'to be' reconstructed by Rix as *b^hu̯eh₂- (vs. *b^huh_x- espoused by other scholars).