Koskinen, K. T., and M. J. Vilenius. “STEADY STATE AND DYNAMIC CHARACTERISTICS OF WATER HYDRAULIC PROPORTIONAL CERAMIC SPOOL VALVE”. International Journal of Fluid Power, vol. 1, no. 1, Mar. 2000, pp. 5-15, https://journals.riverpublishers.com/index.php/IJFP/article/view/653.