I wrote an app for college students researching and writing a paper. It can open most files and website, where you can add highlights to them. Then, you can drag the highlights to its built-in outliner, where you can add comments creating what I call Notes. You can organize the Notes as you wish in the outliner and associate Notes with the sections of the paper you are writing. Finally you can write the the section referring to the relevant Notes while consulting the original file or website with a single click. Nobody bought it. I removed it from Apple's App Store, and I use it daily. It works for me. 13,000 lines of code in my spare time over 5 years. I'm disappointed.