Crystal structure of tetraaqua dinitrato-κ2O,O'-4,4',6,6'-tetramethyl-2,2'- bipyrimidine-κ4N,N':N'',N''' dinickel(II) dinitrate, C6H11N4NiO8 - Ma Ning; Wang Ye (Zeitschrift für Kristallographie - New Crystal Structures, 2014)