Research paper 1

It seems like you're referencing a German PHD thesis - you may have to contact the university? See below link to the record but they seem to only have a print version. Obscure non-english papers / thesis are unlikely to already be digitized and translated. Sometimes you can pay to get them scanned.

I have seen english version of this paper being referenced in a few papers. But can't find it on any of the journals. Thanks for the response btw.

I tried searching an english translation of the name and couldn't find anything. My usual go to is to start with: Google search, google scholar search, and then look for the publisher or university. For newer PHD thesis often universities have public portals where you can download them freely. If it's old and not digitized - you may be able to pay to get it digitized. A previous employer of mine had a library service that would organise this (I'm not entirely sure how it worked but they seemed to be able to pay $20-40 to have old paper-only research papers converted to PDFs)

not sure if you saw this paper - it's not the one you were looking for but looks like some of the formulae or data from the Teferra paper is in it.