N-Doped rGO-sike carbon prepared from coconut shell: structure and specific capacitance by Khambali, Imam, Priyanto, Budhi, Asih, Retno, Baqiya, Malik Anjelh, Ramli, Muhammad Mahyiddin, Osman, Nurul Huda, Tunmee, Sarayut, Nakajima, Hideki, Triwikantoro, Zainuri, Mochamad, Darminto