Husak, M., R. Brajša, and D. Špoljarić. “On the Determination of the Solar Rotation Elements I, Ω and Period Using Sunspot Observations by Ruđer Bošković in 1777”. Rudarsko-geološko-Naftni Zbornik (The Mining-Geological-Petroleum Engineering Bulletin), vol. 36, no. 3, June 2021, doi:10.17794/rgn.2021.3.6.