C.Michael Hogan. 2011. SulfurArquivado em 2012-10-28 no Wayback Machine. Encyclopedia of Earth, eds. A.Jorgensen and C.J.Cleveland, National Council for Science and the environment, Washington DC
C.Michael Hogan. 2011. SulfurArquivado em 2012-10-28 no Wayback Machine. Encyclopedia of Earth, eds. A.Jorgensen and C.J.Cleveland, National Council for Science and the environment, Washington DC