Wu, D., R. Burton, G. Schoenau, and D. Bitner. “MODELLING OF ORIFICE FLOW RATE AT VERY SMALL OPENINGS”. International Journal of Fluid Power, vol. 4, no. 1, Mar. 2003, pp. 31-39, https://journals.riverpublishers.com/index.php/IJFP/article/view/613.