 After Abelard, equipollence and other relations between modal sentences were commonly presented with the help of the square of opposition, which Abelard mentions though it does not appear as such in his works. The square can be taken to refer to de dicto modal sentences or to singular de re modal sentences. Although the distinction between de dicto and de re modal sentences was common in logical treatises on the properties of the terms, syncategorematic terms, and the solution of sophisms, twelfth- and thirteenth-century logicians were mainly interested in the logical properties of singular de re modal sentences. There is no detailed theory of quantified de re modal sentences from this period, and the first movements in this direction by Abelard and his followers were rather confused. A satisfactory theory of de re modal sentences did not appear until the fourteenth century, when the various relations between such sentences was presented by John Buridan in his octagon of opposition.