↑ Abundance of elements in the earth's crust and in the sea, CRC Handbook of Chemistry and Physics, 97th edition (2016–2017), p. 14-17
↑ Commodity Statistics and Information. USGS. All production numbers are for mines, except for Al, Cd, Fe, Ge, In, N, Se (plants, refineries), S (all forms) and As, Br, Mg, Si (unspecified). Data for B, K, Ti, Y are given not for the pure element but for the most common oxide, data for Na and Cl are for NaCl. For many elements like Si, Al, data are ambiguous (many forms produced) and are taken for the pure element. U data is pure element required for consumption by current reactor fleet Lưu trữ 2017-10-01 tại Wayback Machine. WNA.
