Suppose G is a graph and p >= 2q are positive integers. A color-list is a mapping L: V --> P(0, 1,...,p-1) which assigns to each vertex a set L(v) of permissible colors. An L-(p, q)-coloring of G is a (p, q)-coloring h of G such that for each vertex v, h(v) in L(v). We say G is L-(p, q)-colorable if such a coloring exists. A color-size-list is a mapping f: V -->{0, 1, 2,..., p}, which assigns to each vertex v a non-negative integer f(v). We say G is f-(p, q)-colorable if for every color-list L with |{L}(v)| = f(v), G is L-(p, q)-colorable. For odd cycles C, Raspaud and Zhu gave a sharp sufficient condition for a color-size-list f under which C is f-(2k+1, k)-colorable. The corresponding question for even cycles remained open. In this paper, we consider list circular coloring of even cycles. For each even cycle C of length n and for each positive integer k, we give a condition on f which is sufficient and sharp for C to be f-(2k+1, k)-colorable.

A binary clutter is cycling if its packing and covering linear program have integral optimal solutions for all Eulerian edge capacities. We prove that the clutter of odd st- walks of a signed graph is cycling if and only if it does not contain as a minor the clutter of odd circuits of K5 nor the clutter of lines of the Fano matroid. Corollaries of this result include, of many, the characterization for weakly bipartite signed graphs, packing two- commodity paths, packing T-joins with small |T|, a new result on covering odd circuits of a signed graph, as well as a new result on covering odd circuits and odd T-joins of a signed graft.