Ika Putri Sulistiana, Suharyono, Subeki, Medina Alia Rahmawati, Suci Putri Ramadani, and T. Pratami, “Optimization of Fermentation Time and Ghalkoff Microbial Concentration on Organic Robusta Coffee”, Jur. Bio-Geo. Mat. E, vol. 6, no. 2, pp. 97–107, Apr. 2026.