OSCE releases first international report documenting Russia's war crimes
https://www.ukrinform.net/rubric-ato/3456956-jfo-troops-repulse-8-attacks-destroying-11-units-of-equipment-and-artillery-system.html
Report here:
https://www.osce.org/files/f/documents/f/a/515868.pdf
They cite 656 sources which vary from publications by their own organizatin, govt publications, agency publications such as the IAEA, and as you said, twitter, aljazeera, telegram.
https://www.osce.org/odihr/515868
Found a pic:
https://twitter.com/RALee85/status/1514383883114098699