Frearson, P. M., Hardy, D. G., Stern, E. S. (1960). "426. Some new analogues of pethidine. Part IV. Substituents at the 1-position incorporating cyclic ether groups". Journal of the Chemical Society (Resumed): 2103. doi:10.1039/jr9600002103. ISSN0368-1769.
Frearson, P. M., Hardy, D. G., Stern, E. S. (1960). "426. Some new analogues of pethidine. Part IV. Substituents at the 1-position incorporating cyclic ether groups". Journal of the Chemical Society (Resumed): 2103. doi:10.1039/jr9600002103. ISSN0368-1769.