In the smectic A phase, the director field should also satisfy to the association rules of focal conic domains (called law of corresponding cones (l.c.c)) first established by G. Friedel . They have been illustrated in particular in the caption of Figure 4 in the paper  where the authors wrote that "the cyclides of Dupin mesh smoothly onto spheres. The interface is along a cone of generators; the apex of the cone lies on the hyperbola and is the center of the sphere. The apex of the cones of two adjacent focal domains must coincide at this point." These laws have been recently extended . Two adjacent FCDs should have in common a pair of common generatrices as illustrated in the Figure 5a. The branches of the two hyperbolae intersect in two points corresponding to the "poles" of the hyperbolae (see ). These poles both project in the plane of the ellipses onto the same point of the tangent Mt common to the ellipses at M. One can see that the two cones with the two poles as apices and which lies on the ellipses have one common generatrix (blue cones). Also, the two physical branches of the hyperbolae belong to the same cone of revolution (red cone) with apex M, axis Mt. Note that one can go from one layer belonging to FCD1 to one corresponding layer belonging to FCD2 continuously. Figure 5b shows a 2D representation of the l.c.c. Each ellipse possess two focii: one physical called Fi, i=1,2 and one non physical called Fi′. The l.c.c reads as follows: the line F1F2′ goes exactly through the tangency point M of the two ellipses.