Grigg, D. B. (1974). The agricultural systems of the world: An evolutionary approach. Cambridge: Cambridge University Press.
Dyfyniad Arddull ChicagoGrigg, David B. The Agricultural Systems of the World: An Evolutionary Approach. Cambridge: Cambridge University Press, 1974.
Dyfyniad MLAGrigg, David B. The Agricultural Systems of the World: An Evolutionary Approach. Cambridge: Cambridge University Press, 1974.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.