Müller, A.; Krickemeyer, E.; Bögge, H.; Rehder, D. Discrimination Between S²⁻ and SO²⁻ Sites in Mixed Crystal Compounds Containing Co and Co Mo Clusters by ⁵⁹Co-NMR Spectroscopy, and the Relevance for HDS Catalysis. Chimia 1992, 46, 386.