TY  - JOUR
T1  - On the Comparative Value of Certain Geological Ages (or Groups of Formations) considered as Items of Geological Time. 
JF  - Proceedings of the Royal Society of London (1854-1905)
VL  - 22
SP  - 145
EP  - 148
PY  - 1873/01/01/
UR  - http://dx.doi.org/10.1098/rspl.1873.0019
M3  - doi:10.1098/rspl.1873.0019
AU  - Ramsay, A.
ER  -