V. Batchvarov, D. Velinov, and G. Marinova, “Perlite partial substitution of Kieselguhr for beer filtration”, BrSc, vol. 48, no. 11/12, pp. 397–402, Dec. 1995, Accessed: Sep. 28, 2026. [Online]. Available: https://brewingscience.de/index.php/brewingscience/article/view/800