(40)Aggregation-Induced Emission in the Crystals of 9,10-Distyrylanthracene Derivatives: The Essential Role of Restricted Intramolecular Torsion, Jiating He, Bin Xu, Feipeng Chen, Haijian Xia, Kunpeng Li, Ling Ye, Wenjing Tian*, J. Phys. Chem. C, 2009, 113, 9892-9899