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\bibitem{Liu_etal2003} {\textquotedblleft}\textit{The metastable Ni$_{7\pm x}$S$_{6}$ and mixed Ni$_{6\pm x}$(S$_{1-y}$Se$_{y}$)$_{5}$ phases}{\textquotedblright}. Liu Y, Nor{\'e}n L, Withers RL, Hadermann J, Van Tendeloo G, Garcia-Garcia J, Journal of solid state chemistry \textbf{170}, 351 (2003).   http://doi.org/10.1016/S0022-4596(02)00123-8

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