Mioc, Vasile. “ A Better Approximation for Period on Radially Perturbed Orbits”. Rev. Anal. Numér. Théor. Approx. 22, no. 2 (August 1, 1993): 201–205. Accessed September 3, 2025. https://www.ictp.acad.ro/jnaat/journal/article/view/1993-vol22-no2-art10.