Yep, that's exactly it.
You can look through many, many buffy 'verse stories and find examples of exactly this, where an episode is rewritten, and the author then cites the source at the bottom of the chapter.
Using the above as an example:
Say you rewrote Chosen, the series finale for Buffy. You made it fairly different from the episode itself, but it was critical to the chapter to include some of the episode dialogue. At the bottom, you'd have something like this:
*some dialogue from Chosen, Season 7, episode 144.
Although the title of the episode would honestly be sufficient.