On another tack, the problem with permissions...

If you quote, you have to establish whether your source is within copyright, and if so, who owns the copyright. This sort of thing can lead to a detective search.

Case study: I find a scintillating and very quotable letter from Victorian writer and Spiritualist Catherine Crowe to her publisher Robert Chambers. The problem is that it has not been published, and is therefore in copyright. But the letter is in a Kent library, and in typescript form (clearly not its original C19th ms). Where the original might be is unclear.

I take a punt that it might be in the National Library of Scotland. Jim Seccord's recent fascinating study of Chambers and his book 'Vestiges of the History of Creation' (a precursor of Darwin's 'Origin of Species') states the NLS holds Chambers family & business papers.

I contact the NLS and they ask me to cite the opening lines of the letter. Hurray! they hold it, but they don't own the copyright. The person who does has recently died. But they will try and find out who the new copyright holder might be.

How like a detective novel.