A relatively fixed factor of production such as land (today we would include all natural resources) can not produce positive feedback for exponential growth. (science.sciencemag.org)
It also assumes that there are four major factors of production in an economy and that all revenues must go to one of these four sources. (investopedia.com)
The British founders of modern economics argued that capital and labor are also important factors of production. (religion-online.org)