TY  - RPRT
TI  - Stratigraphic significance and petrology of phosphate nodules at base of Niobrara Formation, east flank of Black Hills, South Dakota
AU  - H. A. Tourtelot
AU  - W. A. Cobban
PY  - 1968
DO  - 10.3133/pp594l
UR  - https://pubs.usgs.gov/publication/pp594L
ID  - pp594L
ER  -