The Hidden Twilight, and the one related to Unearthed. I have constantly been doing these Research quest for Neloth in hope that The Hidden Twilight will pop up. Can anyone please give me a hint or some help with starting these quest???? Thank you.

There is one If you do a Quest For the Mining Guy outside of Raven Rock (15 thousand gold to complete it and get the book)
There is one in Tel Mithryn (When you can use the Staff Enchanter)
There are 2 in the main quests.

And there is one more for helping him after you have talked to the skall