A comparison of the floras of the Colchester (No.2) Coal and Francis Creek Shale. (In: Depositional environments in parts of the Carbondale Formation: Western and northern Illinois)
Reference:
Peppers,R.A. et al. (1970)
A comparison of the floras of the Colchester (No.2) Coal and Francis Creek Shale. (In: Depositional environments in parts of the Carbondale Formation: Western and northern Illinois) Illinois State Geological Survey, Guidebook Series
# 8 P. 61- 74