M.  Majumder, Choudhary, R. Bilash, Thakur, A. K., and Karbhal, I., ?Impact of rare-earth metal oxide (Eu 2 O 3 ) on the electrochemical properties of a polypyrrole/CuO polymeric composite for supercapacitor applications?, RSC Advances, vol. 7, no. 32, pp. 20037-20048, 2017.