Francis, C., Baltensperger, D., Dick, W., Roberts, C., Logsdon, S., Savin, M., . . . Al-Amoodi, L. (2009). Organic farming: The ecological system. Wisconsin, Estados Unidos: American Society of Agronomy ; Crop Science Society of America ; Soil Science Society of America.

Francis, Charles,, David Baltensperger, Warren Dick, Craig Roberts, Sally Logsdon, Mary Savin, Hari Krishnan, April Ulery, and Lisa Al-Amoodi. Organic Farming: The Ecological System. Wisconsin, Estados Unidos: American Society of Agronomy ; Crop Science Society of America ; Soil Science Society of America, 2009.

Francis, Charles,, et al. Organic Farming: The Ecological System. Wisconsin, Estados Unidos: American Society of Agronomy ; Crop Science Society of America ; Soil Science Society of America, 2009.