Dark Corner - Plants Feel
- Offers information on how plants can read human minds.
- http://www.angelfire.com/clone2/darkcorner/plantsfeel.html

Plant Articles by Judith Handelsman
- A series of articles from various magazines. The second one has relevance primary perception discoveries, as it describes Handelsman's own experiences with the phenomenon.
- http://here-and-now.org/judith/articles.html

Vignettes From the History of Plant Morphology
- Articles about people, mostly Agnes Arber, who created unconventional theories about plant morphology.
- http://members.aol.com/cefield/hauke/contents.html

Subtle Energy
- An article in a web-based magazine by Paul von Ward Lightworks. Deals with Cleve Backster's mind-plant discoveries and the author's speculations about them.
- http://www.lightworks.com/MonthlyAspectarian/1998/May/0598-05.htm

Chapter Six- Cleve Backster's Laboratory
- A chapter in a web-based book by psychologist Ingo Swann. Deals with a trip made by Swann to Backster's laboratory and chronicles the first-hand experiment he witnessed.
- http://www.biomindsuperpowers.com/Pages/RealStoryCh6.html