Psychedelic drugs: steric factors that predict psychotropic activity. Proc Natl Acad Sci U S A May 1, 1968 S H Snyder, E Richelson 51 citations Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans the biological, physical, and social sciences. DOI: 10.1073/pnas.60.1.206 (opens in new tab) Full text (opens in new tab)