Esther M. Arkin Michael A. Bender Erik D. Demaine Sándor P. Fekete Joseph S. B. Mitchell Saurabh Sethia Optimal Covering Tours with Turn Costs. 531-566 2005 35 SIAM J. Comput. 3 http://epubs.siam.org/SICOMP/volume-35/art_43426.html db/journals/siamcomp/siamcomp35.html#ArkinBDFMS05