Pavol Federl Przemyslaw Prusinkiewicz Solving Differential Equations in Developmental Models of Multicellular Structures Expressed Using L-systems. 65-72 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3037&spage=65 2004 conf/iccS/2004-2 International Conference on Computational Science db/conf/iccS/iccS2004-2.html#FederlP04