Mary V. Ashley Tanya Y. Berger-Wolf Wanpracha Art Chaovalitwongse Bhaskar DasGupta Ashfaq A. Khokhar Saad I. Sheikh On Approximating an Implicit Cover Problem in Biology. 43-54 2009 AAIM http://dx.doi.org/10.1007/978-3-642-02158-9_6 conf/aaim/2009 db/conf/aaim/aaim2009.html#AshleyBCDKS09