@article{Borowiecki:2012,
  author  = "M. Borowiecki and E. Drgas-Burchardt",
  title   = "Acyclic homomorphisms to stars of graph Cartesian products and chordal bipartite graphs",
  journal = "Discrete Mathematics",
  volume  = "Vol. 312",
  number  = "no 14",
  pages   = "2146--2152",
  year    = "2012",
}