I also saw "study," but I think the Spanish would have used the obvious translation of "estudio". I ran a search for the author's name + internal + external and find that they like that juxtaposition a lot. Also mentioned, besides internal/external collective memories, are internal/external reconciliation and others that definitely don't apply. I'm going to stick with my answer, even though it seems odd, because it's specifically mentioned in the abstract. I've also provided a link to the author's long explanation of the meaning and consequences of 'self-censorship' and 'external censorship'. What it means, essentially, is filtering out what we don't want to look at to burnish our memory of events.
https://tinyurl.com/y396gq58