ISBN 9780878573417. ↑ "History". Square Foot Gardening. Retrieved 2021-02-15. ↑ Pongsiri, Montira J.; Roman, Joe; Ezenwa, Vanessa O.; Goldberg, Tony L.; Koren, Hillel S.; Newbold, Stephen C.; Ostfeld, Richard S.; Pattanayak, Subhrendu K.; Salkeld, Daniel J. (2009).