Lark, Tyler J.; Meghan Salmon, J.; Gibbs, Holly K. (2015). «Cropland expansion outpaces agricultural and biofuel policies in the United States». Environmental Research Letters10 (4): 044003. Bibcode:2015ERL....10d4003L. doi:10.1088/1748-9326/10/4/044003.
Lark, Tyler J.; Meghan Salmon, J.; Gibbs, Holly K. (2015). «Cropland expansion outpaces agricultural and biofuel policies in the United States». Environmental Research Letters10 (4): 044003. Bibcode:2015ERL....10d4003L. doi:10.1088/1748-9326/10/4/044003.