Spin‐Crossover Fe<sup>II</sup><sub>4</sub> Squares: Two‐Step Complete Spin Transition and Reversible Single‐Crystal‐to‐Single‐Crystal TransformationRong‐Jia Wei, Lan‐Sun Zheng, Rong‐Bin Huang et al.|Angewandte Chemie International Edition|2011Cited by 134