Premise: Avatar : The Last Airbender ( Avatar : The Legend of Aang in some regions ) is an American animated television series that aired for three seasons ( referred to as `` books '' in each episode 's title card ) on Nickelodeon from 2005 to 2008 .
Hypothesis: Avatar: The Last Airbender's episodes were referred to as "books" on the show.
Label: ENTAILMENT