Kuepper, George and Mardi Dodson. 2001. Companion Planting: Basic Concepts and Resources. ATTRA. Accessed at: <https://attra.ncat.org/attra-pub/summaries/summary.php?pub=72>
Companion Planting: Basic Concepts and Resources was published in 2008 by the National Sustainable Agriculture Information Service (ATTRA,) which provides farmers and educators information on sustainable agricultural practices, and was written by George Kuepper and Mardi Dodson. This publication looks at companion planting as a way to increase the biodiversity of agroecosystems in both home and market gardens. The authors define companion planting as the establishment of two or more plant species in close proximity so that some cultural benefit (pest control, higher yield, etc.) is derived. The Companion planting chart provided in this publication lists the crop variety, its companions as well as its incompatible varieties. A scientific foundation for companion planting and resources are provided after the chart. Ancient Companions, An Appendix to Companion Planting: Basic Concepts & Resources by Mardi Dodson is also attached at the end. It discusses the foundation for the three sisters: corn, bean, and squash.