Baird, Gordon (1986). "Taphonomy of Middle Pennsylvanian Mazon Creek area fossil localities, northeast Illinois: Significance of exceptional fossil preservation in syngenetic concretions". PALAIOS. 1 (3): 271–285. Bibcode:1986Palai...1..271B. doi:10.2307/3514690. JSTOR3514690.
Baird, Gordon (1986). "Taphonomy of Middle Pennsylvanian Mazon Creek area fossil localities, northeast Illinois: Significance of exceptional fossil preservation in syngenetic concretions". PALAIOS. 1 (3): 271–285. Bibcode:1986Palai...1..271B. doi:10.2307/3514690. JSTOR3514690.
Baird, Gordon (1986). "Taphonomy of Middle Pennsylvanian Mazon Creek area fossil localities, northeast Illinois: Significance of exceptional fossil preservation in syngenetic concretions". PALAIOS. 1 (3): 271–285. Bibcode:1986Palai...1..271B. doi:10.2307/3514690. JSTOR3514690.