We would like to thank Roni Rosenfeld and his LM96 group for making crucial resources available. Thanks are also due Mari Ostendorf and Patti Price for helpful discussions and comments. This research was supported in part by the Advanced Research Projects Agency under NSF Grant IRI-9314967. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Advanced Research Projects Agency or the National Science Foundation.