“…Let us observe that, as a trivial consequence of the monotonicity (1) , the higher the Hamiltonian's degree the larger the corresponding set of MRFs. Furthermore, as shown in an example in [29], for k sufficiently large it can well happen that a smooth degree-k MRF does exist while a standard, i.e. degree-1, C 1 MRF, does not (see also [28,Ex. 2.1-2.4], for the case with no cost).…”