olemus
ISO/IEC TR 18120:
digitaalsisu struktureeritud agregaat,
mis kasutab raamatulugerit ning
on mõeldud toetama õpi-, haridus- ja koolitustegevusi
=
structured aggregation of digital content intended to support learning, education and training (LET) activities and which uses an e-textbook reader

ülevaateid
https://en.wikipedia.org/wiki/Digital_textbook

https://www.slideserve.com/asher/should-you-buy-an-e-textbook-powerpoint-ppt-presentation

https://kitaboo.com/about-digital-textbooks/

https://journals.ala.org/index.php/ltr/article/view/4426/5143

http://ceur-ws.org/Vol-2384/paper05.pdf

https://researchonline.nd.edu.au/cgi/viewcontent.cgi?article=1211&context=theses

näiteid
https://duckduckgo.com/?q=e-textbook&t=h_&iax=images&ia=images