"BGH zur Reduzierung der Einspeiseleistung von Photovoltaikanlagen" [Reduction of the feed-in power of solar Systems]
"Erneuerbare Energien Magazin, Ausgabe 03/2020 (April | Mai), S. 57" [Renewable Energy Magazine, issue 03/2020 (April | May), p. 57]
Here you can find the article (only available in German language).