Martins, A.F., Morais, A.B. de and Baron, G.M. 1984. Application of extractive spectrophotometric methods for determination of trace elements of ambiental relevance in the thermoeletric coal from Candiota, RS. Ciência e Natura. 6, 6 (Dec. 1984), 75–82. DOI:https://doi.org/10.5902/2179460X25071.