Ersteniuk, Y. ., Gasyuk, I. ., Boryschak, A. ., & Yakubovskyi, P. . (2020). Methodology of Problems Creation and Selection for Astronomy Olympiads on Example of Tasks on the Topic of Kepler’s Laws . Journal of Vasyl Stefanyk Precarpathian National University, 7(1), 156–165. https://doi.org/10.15330/jpnu.7.1.156-165