The simplest graph drawing method is that of putting the vertices of a graph on a line (spine) and drawing the edges as half-circles on k half planes (pages). Such drawings are called k-page book drawings and the minimal number of edge crossings in such a drawing is called the k-page crossing number. In a one-page book drawing, all edges are placed on one side of the spine, and in a two-page bo...

An oriented k-coloring of an oriented graph G is a mapping c : V (G) → {1, 2, . . . , k} such that (i) if xy ∈ E(G) then c(x) 6= c(y) and (ii) if xy, zt ∈ E(G) then c(x) = c(t) =⇒ c(y) 6= c(z). The oriented chromatic number ~ χ(G) of an oriented graph G is defined as the smallest k such that G admits an oriented k-coloring. We prove in this paper that every Halin graph has oriented chromatic nu...