Kuehnlein, M., J. Ewald, H. Murrenhoff, and J. Ewald. “ADJUSTABLE FLOW-CONTROL VALVE FOR THE SELF-ENERGISING ELECTRO-HYDRAULIC BRAKE”. International Journal of Fluid Power, vol. 13, no. 2, Aug. 2012, pp. 5-14, https://journals.riverpublishers.com/index.php/IJFP/article/view/233.