The Wild Hunt - Acquiring all the Journal Entries
The conversation with Dandelion after triggering the flashback, after talking to Ciaran, I don't know how to reliably acquire. It adds a unique journal entry, but I don't know what you must (or must not) do prior to talking to Dandelion. As I mention in the thread I linked to above, my only theory so far is to not
talk to Dandelion at all, prior to triggering the flashback of the Isle of Avallach (interrogating Ciaran).
The manuscript of Morten Collis is found in the catacombs outside Vergen, during Chapter 2. It's in one of the wrapped-up corpses. Showing this to either Philippa or Síle, will enable you to talk to Cynthia or Myron about this script; you can also later, after getting the flashback about the Ravine of the Hydra, show it to Dandelion, but he falls asleep because it's so boring. He is instead more interested in the Song of the Hunt - once you've found this book, and have the Ravine of the Hydra flashback trigger, have Dandelion interpret the poem for you. As far as I know, this can only be done if you're on Roche's path, however, probably due to a bug. I opened up the topic I linked to in an attempt to decipher the different requirements for unlocking all the journal entries concerning the Wild Hunt.