@conference {Horvath07d, title = {A {\textquoteright}gas of Circles{\textquoteright} Phase Field Model and its Application to Tree Crown Extraction}, booktitle = {Proceedings of the European Signal Processing Conference (EUSIPCO)}, year = {2007}, month = {2007}, type = {Conference paper}, address = {Poznan, Poland}, author = {Peter Horvath and Ian Jermyn}, editor = {Marek Domanski and Ryszard Stasinski and Maciej Bartkowiak} }