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\bibitem{Krekels_etal1993} {\textquotedblleft}\textit{SO$_{4}$-chain formation and ordering in [YSrCa]Sr$_{2}$Cu$_{2.78}$(SO$_{4}$)$_{0.22}$O$_{7-\delta}$}{\textquotedblright}. Krekels T, Milat O, Van Tendeloo G, van Landuyt J, Amelinckx S, Slater PR, Greaves C, Physica: C : superconductivity \textbf{210}, 439 (1993).   http://doi.org/10.1016/0921-4534(93)90988-3

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