“Efek Variasi Waktu Dan Jumlah Lilitan Pada Sistem Filter Elektromagnetik Terhadap Penurunan Kadar Pb, Zn Dan Co: (Effects of Time Variation and Number of Turns in Electromagnetic Filter Systems on Decreasing Levels of Pb, Zn and Co)”. 2020. Gravitasi 19 (2): 40-43. https://doi.org/10.22487/gravitasi.v19i2.15357.