Ismail, A. I., et al. “On the Existence of Periodic Solutions of a Gyrostat Similar to Lagrange’s Gyroscope”. Technische Mechanik - European Journal of Engineering Mechanics, vol. 20, no. 4, Oct. 2019, pp. 295-04, https://journals.ub.ovgu.de/index.php/techmech/article/view/1105.