@inproceedings{
author={Juul Jesper},
year={2003},
title={The game, the player, the world: looking for a heart of gameness},
isbn={ISSN 2342-9666},
booktitle={DiGRA \&\#3903 - Proceedings of the 2003 DiGRA International Conference: Level Up},
url={http://www.digra.org/wp-content/uploads/digital-library/05163.50560.pdf}
}