Cahyadi, Adha, et al. “An Extended Kalman Filter for Nonsmooth Attitude Control Design of Quadrotors Using Quaternion Representation”. Indonesian Journal of Electrical Engineering and Informatics (IJEEI), vol. 10, no. 2, June 2022, pp. 480-8, https://doi.org/10.52549/ijeei.v10i2.3532.