Elsaed, Essam, and Matti Linjama. “A Review of Pilot-Operated Hydraulic Valves – Development, Challenges, and a Comparative Study”. International Journal of Fluid Power 24, no. 04 (November 7, 2023): 683–724. Accessed May 13, 2024. https://journals.riverpublishers.com/index.php/IJFP/article/view/15013.