Verma , Surendra P. 1998. «Improved Concentration Data in Two International Geochemical Reference Materials (USGS Basalt BIR-1 and GSJ Peridotite JP-1) by Outlier Rejection». Geofísica Internacional 37 (3):215-50. https://doi.org/10.22201/igeof.00167169p.1998.37.3.394.