Psychological effects of (S)-ketamine and N,N-dimethyltryptamine (DMT): a double blind, cross-over study in healthy volunteers. - Gouzoulis-Mayfrank,E.; Heekeren,K.; Neukirch,A.; Stoll,M.; Stock,C.; Obradovic,M.; Kovar,K-A. (Pharmacopsychiatry, 2005)