[...] {RIGHT, LEFT}-ANCHOR (S1, S2): Any element at the designated periphery of S1 has a correspondent at the designated periphery of S2. Let "Edge"(X, {L, R}) = the element standing at the "Edge" = L, R of X. RIGHT-ANCHOR. iF X = Edge(S1, R) and "y" = Edge (S2, R) then xℜy. LEFT-ANCHOR. Likewise, "mutatis mutandis". - McCarthy & Prince (2004), a pag.435