Crystal structure of tetraaqua(4,4’-bipyridine-N,N’)nickel(II) fumarate tetrahydrate, Ni(H2O)4(C10H8N2)(C4H2O4) · 4H2O - Zheng Y.-Q.; Kong Z.-P.; Lin J.-L. (Zeitschrift für Kristallographie - New Crystal Structures, 2002)