Andreeva, O., and V. Malashchuk. “Results of 20-Year Solar Observations in the He I λ 1083 Nm Line at the Crimean Astrophysical Observatory”. Acta Astrophysica Taurica, vol. 5, no. 2, June 2024, pp. 21-24, https://astrophysicatauricum.org/index.php/aat/article/view/82.