Bahtiar, A., and K. Habibie. “THE STABILITY STUDIES OF MIXED HALIDE PEROVSKITE CH3NH3PbBrXI3-X THIN FILMS IN AMBIENT WITH AIR HUMIDITY 70% USING UV-VIS SPECTROSCOPY AND X-RAY DIFFRACTION”. Spektra: Jurnal Fisika Dan Aplikasinya, Vol. 5, no. 2, Aug. 2020, pp. 109 -18, doi:10.21009/SPEKTRA.052.03.