* [https://pubs.usgs.gov/periodicals/mcs2021/mcs2021-chromium.pdf «Chromium Statistics and Information». U.S. Geological Survey (en [[anglés]])] | * [https://pubs.usgs.gov/periodicals/mcs2021/mcs2021-chromium.pdf «Chromium Statistics and Information». U.S. Geological Survey (en [[anglés]])] |