USGS professional paper · 1957 · 150 citations · 21 references
ROCKS, NAVAJO COUNTHY stone of the San Rafael group. The Cow Springs also intertongues with the lower members of the Morrison formation.
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Manual of Sedimentary Petrography
Erik Stoklund Larsen · Science · 1939 · 665 citations
Persistence of Heavy Minerals and Geologic Age
F. J. Pettijohn · The Journal of Geology · 1941 · 213 citations