Etienne de Klerk Dmitrii V. Pasechnik Renata Sotirov On Semidefinite Programming Relaxations of the Traveling Salesman Problem. 1559-1573 2008 19 SIAM J. Optim. 4 https://doi.org/10.1137/070711141 https://www.wikidata.org/entity/Q56874368 db/journals/siamjo/siamjo19.html#KlerkPS08