Board Thread:Shingeki no Kyojin Wiki/@comment-5774380-20150329004214/@comment-5774380-20150329040129

@PrelateZeratul: Yes, that's what I'm talking about.

@EternalLocket: I mean their own articles. For example, Sudden Visitors is not canon, but it has its own article; though the events in it are not used to write character's biographies and other stuff.

Ilse's Notebook is part of the manga, so it is canon, but No Regrets and Before the Fall no, since they were not written by Isayama and we have no confirmation that they were approved by him as canon parts of the same timeline of the manga.