@article{cats9-5,
  author{Nutan Limaye, Meena Mahajan and Prajakta Nimbhorkar},
  title={Longest Paths in Planar DAGs in Unambiguous Log-Space}
  journal={Chicago Journal of Theoretical Computer Science},
  volume={2010},
  number={8},
  publisher={University of Chicago},
  month={June},
  year={2010}
}