US patent 3557127, Satzinger, G., "Substituted Cyclohexenes, Derivatives thereof and Processes for Obtaining Same", issued 19. 1. 1971.
nih.gov
ncbi.nlm.nih.gov
Schulz, R.; Bläsig, J.; Wüster, M.; Herz, A. (1978). „The Opiate-Like Action of Tilidine is Mediated by Metabolites”. Naunyn-Schmiedeberg's Archives of Pharmacology. 304 (2): 89—93. PMID212687.