International audience Three Greek manuscripts of the Coislin Collection in the French National Library (C.20, 21, 22), written in the Xth-XIth centuries, show a similar text : the four Gospels framed by Petrus of Laodicea's catena. The layout of the three glosses is a three-sided framing catena but their detailed examination reveals different principles: an economical use of the scroll and a concern for symmetry in the case of C.20; adequacy between text and commentary in the case of the two others. The ruling which has prepared the layout shows another order : the different extension of the ruled lines of the commentary (compared with the biblical text) concerns only the upper and lower parts of the page, on a number of the folios of C.22, whereas all areas of the commentary are concerned on the two other manuscripts.