K. Halder, B. K. Paul, B. Bagchi, A. Bhattacharya, and S. Das, “Copper Ion Doped Mullite Composite in Poly (vinylidene Fluoride) Matrix: Effect on Microstructure, Phase Behavior and Electrical Properties”, J. Res. Updates Polym. Sci., vol. 3, no. 3, pp. 157–169, Oct. 2014.