Rexfort, A.; Mutterlose, J. (2006). "Stable isotope records from Sepia officinalis — a key to understanding the ecology of belemnites?". Earth and Planetary Science Letters247 (3–4): 212. doi:10.1016/j.epsl.2006.04.025. Bibcode: 2006E&PSL.247..212R.
Rexfort, A.; Mutterlose, J. (2006). "Stable isotope records from Sepia officinalis — a key to understanding the ecology of belemnites?". Earth and Planetary Science Letters247 (3–4): 212. doi:10.1016/j.epsl.2006.04.025. Bibcode: 2006E&PSL.247..212R.