Perry, Leonard. "Interesting cool crops". University of Vermont Extension, Department of Plant and Soil Science. Diarsipkan dari versi asli tanggal 2022-06-19. Diakses tanggal 5 June 2018.
Perry, Leonard. "Interesting cool crops". University of Vermont Extension, Department of Plant and Soil Science. Diarsipkan dari versi asli tanggal 2022-06-19. Diakses tanggal 5 June 2018.