Colina, M., P. H. Gardiner, Z. Rivas, and F. Troncone. “Modified Procedure for the Simultaneous Determination of Nitrogen, Phosphorus and Sulphur by Hydrogen Peroxide Microwave Digestion and Ion Chromatography”. Ciencia, Vol. 14, no. 1, 1, http://www.produccioncientificaluz.org/index.php/ciencia/article/view/9316.