1. Akhtemov, Z.S., Perebeinos, V.A., Shtertser, N.I., Giant coronal hole of 2015–2017. II: Relation between magnetic field, active solar regions, and flares, Izv. Krym. Astrofiz. Obs., 2018, vol. 114, no. 1, pp. 123–128.
2. Andreeva, O.A. and Malashchuk, V.M., The changing in the vertical boundaries of a giant coronal hole, Astron. Astrophys. Trans., 2019, vol. 31, no. 2, pp. 209–216.
3. Andreeva, O.A., Malashchuk, V.M., Akhtemov, Z.S., and Zhigalkin, R.K., Variations in the area and intensity of a giant coronal hole, Izv. Krym. Astrofiz. Obs., 2018, vol. 114, no. 1, pp. 129–134.
4. Andreeva, O.A., Akhtemov, Z.S., Malashchuk, V.M., and Zhigalkin, R.K., Study of variations of some characteristics of the giant coronal hole of 2015–2017, Geomagn. Aeron. (Engl. Transl.), 2018, vol. 58, no. 8, pp. 916–924.
5. Badalyan, O.G., Obridko, V.N., and Sýkora, Yu., Cyclic variations in the differential rotation of the solar corona, Astron. Rep., 2006, vol. 50, no. 4, pp. 312–324.