Research - Defining Game Immersion

The first thing that must be identified is; what is immersion in the context of games. Initial searches were to try and pin down the definition of immersion in the study of games. 
The following paper was added to my research list from the search:
A Grounded Investigation of Game Immersion, Brown. E, Cairns. P, (2004). 
[Can be accessed here: http://www-users.cs.york.ac.uk/~pcairns/papers/Immersion.pdf ]

An analysis of this paper will follow which will include any supporting/related papers.