S. Permana, S. F. Vincia, A. Amilia, A. Maksum, K. S. Widana, and J. W. Soedarsono, “Enrichment on Bangka tin slag’s tantalum and niobium oxide contents through non-fluoride process”, EEJET, vol. 5, no. 12 (95), pp. 56–64, Oct. 2018.