This is an old revision of the document!

http://ntrs.nasa.gov/search.jsp?R=808899id=2&qs=No%3D30%26Ntt%3Dwolverton%26Ntk%3DAuthorList%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1

http://ntrs.nasa.gov/search.jsp?R=794747 id=4&qs=No%3D30%26Ntt%3Dwolverton%26Ntk%3DAuthorList%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1

“Plants that top the clean-air list include peace lily, bamboo palm, English ivy, mums, and gerbera daisies” http://www.treehugger.com/files/2007/12/belair_filterin_1.php