- https://www.reuters.com/article/serbia-kosovo-energy/serbia-kosovo-power-grid-row-delays-european-clocks-idUSL5N1QP2FF
- https://www.entsoe.eu/news-events/announcements/announcements-archive/Pages/News/2018-03-06-press-release-continuing-frequency-deviation-in-the-continental-european-power-system.aspx
- https://wysokienapiecie.pl/8656-kto-ukradl-prad-za-3-mln-euro-spowolnil-europejskie-zegary/
- https://www.swissgrid.ch/swissgrid/en/home/experts/topics/frequency.html