Article thematizing two properties (circadian and eutark*) of digital yet sustainable digital education devices has been just accepted for publication in 7th volume of "Fachmagazin für Digitalisierung in der Lehr Synergie". Publication date is 22 May 2019 (AE490522). 

*word "eutark" is not a typo but a neologism meaning "energy-autark", i.e. "able to produce energy necessary for own operation"