References
- British Geological Survey . 1981 . UK Mineral Statistics, Annual to 1984 , Brussels : International Iron and Steel Institute (IISI), Chromium and the Steel Industry .
- International Iron and Steel Institute (IISI) . 1985 . Vanadium, Niobium, Molybdenum and the Steel Industry , Brussels 1984 Washington : US Bureau of Mines, Mineral Facts & Problems .