1. “Original close-packed structure and magnetic properties of the Pb_4Mn_9O_20 manganite”. Abakumov AM, Hadermann J, Tsirlin AA, Tan H, Verbeeck J, Zhang H, Dikarev EV, Shpanchenko RV, Antipov EV, Journal of solid state chemistry 182, 2231 (2009).   http://doi.org/10.1016/j.jssc.2009.06.003