Three focussharing conicsdefine a quadrangle of intersections of common chords (Neville's theorem). Here, the black circle is the absolute conic. The notation is exemplified by: F_{1} is the focus common to K_{2} and K_{3}, d_{21} is the directrix of K_{2} to the focus F_{1}. The central part is enlarged to see the quadrangle of intersections of the common chords connecting opposite intersections of the conics.

