Further examples of non-positively curved 2-dimensional complexes of groups have been constructed by Swiatkowski based on actions simply transitive on oriented edges and inducing a 3-fold symmetry on each triangle; in this case too the complex of groups is obtained from the regular action on the second barycentric subdivision. The simplest example, discovered earlier with Ballmann, starts from a finite group "H" with a symmetric set of generators "S", not containing the identity, such that the corresponding Cayley graph has girth at least 6. The associated group is generated by "H" and an involution τ subject to (τg)3 = 1 for each "g" in "S".