Ah, the Forbidden Oasis. Forbidden for a reason, perhaps? Once the site of a bustling mining organization, all you will find here nowadays is sand... and plenty of it. The oasis is a welcome life-spring in an otherwise inhospitable desert, but also holds its share of secrets and of course, tears in the veil.
Letters & Notes #68 - The Marker
Claim "The Marker" landmark to the south of the Desert Camp.
Letters & Notes #11 A Miner's Journal
To the left of the Desert Camp, when you run into the stone wall, in a small camp.
Letters & Notes #70 - The Weight of War
Gained when claiming "The Weight of War" landmark, to the east of Desert Camp.
History #79 - Worn Pillars
Gained when claiming the "Worn Pillars" landmark.
Letters & Notes #61 - Spiral Mine
Found by claiming the "Spiral Mine" landmark.
Letters & Notes #48 - Mysterious Book
Found while exploring the highest reaches of the area (likely while shard hunting) between the two camps. You will need to energize a walkway between two cliff-tops at one point and can find this book on the second cliff-top past the newly formed walkway.
Letters & Notes #71 - Tracing from Temple Doors
Found while doing the main quest in this area, "The Temple of Pride".
Found in Solasan. Use the Veilfire then backtrack across the hall to find the Glyph.
An Apostate's Message
This is a Glyph found in the Spiral Mine, you'll need to enter at the west end of the bottom layer to reach it. The place is dark with lots of braziers along the way.