“…In Riemannian spaces, biharmonic curves and, more generally, biharmonic maps, were examined quite in detail (see [6], [8], [12], [13], [14], [17], [18], [19]). As a first remark, geodesics of ∇ are always biharmonic (actually, they are minimum points for the bienergy), but the converse is generally not true.…”