If Otto relies on his notebook, what this comes to is that Otto himself is best regarded as an extended system, a coupling of biological organism and external resources.
Gist of Idea
If a person relies on their notes, those notes are parted of the extended system which is the person
A Clark / D Chalmers (The Extended Mind , §5)
You start to get giddy as you read this stuff. If two people constantly share a notebook, they begin to blend into one another. It inclines me towards a more 'animalist' view of the nature of a person or a self.
-: 'Analysis' [-], p.8