  We give the resolutions of co-letterplace ideals of posets in a completely
explicit, very simple form. This generalizes and simplifies a number of linear
resolutions in the literature, among them the Eliahou-Kervaire resolutions of
strongly stable ideals generated in a single degree. Our method is based on a
general result of K. Yanagawa using the canonical module of a Cohen-Macaulay
Stanley-Reisner ring. We discuss in detail how the canonical module may
effectively be computed, and from this derive directly the resolutions.
  A surprising consequence is that we obtain a large class of simplicial
spheres comprehensively generalizing Bier spheres.
