Amotz Bar-Noy Panagiotis Cheilaris Michael Lampis Valia Mitsou Stathis Zachos Ordered Coloring Grids and Related Graphs. 30-43 2009 SIROCCO http://dx.doi.org/10.1007/978-3-642-11476-2_4 conf/sirocco/2009 db/conf/sirocco/sirocco2009.html#Bar-NoyCLMZ09