<hi xmlns="http://www.tei-c.org/ns/1.0" rend="bold">Hammersley, John M. / Clifford, Peter</hi> (1971): <hi xmlns="http://www.tei-c.org/ns/1.0" rend="italic">Markov fields on finite graphs and lattices</hi>.  <ref xmlns="http://www.tei-c.org/ns/1.0" target="http://www.statslab.cam.ac.uk/~grg/books/hammfest/hamm-cliff.pdf">http://www.statslab.cam.ac.uk/~grg/books/hammfest/hamm-cliff.pdf</ref>.