Sumaruk, Y. 2011. Long-term changes in the geomagnetic field from observational data at magnetic observatories of Ukraine. Geofizicheskiy Zhurnal. 33, 5 (Oct. 2011), 120–127. DOI:https://doi.org/10.24028/gzh.0203-3100.v33i5.2011.116873.