Glenn Hickey Paz Carmi Anil Maheshwari Norbert Zeh NAPX: A Polynomial Time Approximation Scheme for the Noah's Ark Problem. 76-86 2008 WABI http://dx.doi.org/10.1007/978-3-540-87361-7_7 conf/wabi/2008 db/conf/wabi/wabi2008.html#HickeyCMZ08