Ober Joyce A & U.S. Geological Survey. 2005 minerals yearbook , sulfur.
Cita Chicago (17th ed.)Ober Joyce A i U.S. Geological Survey. 2005 Minerals Yearbook , Sulfur.
Cita MLA (9th ed.)Ober Joyce A i U.S. Geological Survey. 2005 Minerals Yearbook , Sulfur.
Atenció: Aquestes cites poden no estar 100% correctes.