IEEE is a Digital Library (DL) that it is hugely used in Computer Science. I think that it should be added as a possible target.
In this case, it is not recognized the DOI in HTML nor PDF version and it has some extra difficulties do to how is this DL implemented to annotate the PDF version (see below).
Use this article as an example:
https://ieeexplore.ieee.org/document/6916375
For HTML
Try to resolve the DOI. It can be retrieved when navigating from DOI URL:
https://doi.org/10.1109/U-MEDIA.2014.59
Or it is possible to scrap from the website, it appears usually in this place:
![image](https://user-images.githubusercontent.com/6429012/67192783-790d5f00-f3f4-11e9-992a-3d2aeea9c426.png)
For PDF
Augment PDF download icon with the DOI scraped in previous step. When user clicks on PDF document, it is redirected to a new URL:
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6916375#doi:10.1109/U-MEDIA.2014.59
It cannot be annotated, as the PDF is inside an iframe. A new redirection must be supported (or automatically opened), maintaining the #doi:10.1109/U-MEDIA.2014.59 in the URL of the iframe.
This is already implemented in Highlight&Go. See this file.