Moelyadi, M. A., H. A. Putra, and G. Sachs. “Unsteady Aerodynamics of Flapping Wing of a Bird”. Journal of Engineering and Technological Sciences, vol. 45, no. 1, Apr. 2013, pp. 47-60, doi:10.5614/j.eng.technol.sci.2013.45.1.4.