M. Bashir I. Kassim and T. A.W. Khmis, “Production of the polysaccharid ‘Xanthan’ by Mixed Cultures of the Bacterium Xanthomonas campestris ATCC 13951 and the Yeast Kluyveromyces lactis EMCC 9 from Whey Milk”, RSCI, vol. 16, no. 10, pp. 158–171, Aug. 2005.