Logic

What is the earliest printed book on logic? meaning the first which gives the common theory of the syllogism. Does it contain the celebrated words *Barbara, Celarent*, &c. The difficulty will probably arise from this, that each book has some *undated* editions which are probably earlier than the dated ones. Of books with dates there is the exposition of Petrus Hispanus by Joh. Versor, in 1473, and the *Summulæ* of Paulus Venetus, in 1474; the first I find in Hain (who had not seen it), the second I have seen. Can any one of your readers go farther back?