Dykha, M., Hetman, M., Dytyniuk, V., & Makovkin, O. (2026). Experimental and Analytical Study of Acid Number Variation in Engine Oils Under Operational Contamination. Problems of Tribology, 31(1/119), 48–55. https://doi.org/10.31891/2079-1372-2026-119-1-48-55