Has anyone seen a copy of the above?

It is referenced in the Catholic Encyclopedia article, 'Music of the Mass':
"Still another method is that of Giulio Bas who has compiled a volume, "Gradualis Versus Alleluia et Tractus" (Dusseldorf, 1910), of plainsong settings from the Ambrosian, Aquileian, Greek, Mozarabic chant, for Sundays and Double Feasts in order to facilitate the rendering of the more difficult portions of the Proper."