Tony Griffiths Alvaro A. A. Fernandes Norman W. Paton Keith T. Mason Bo Huang Michael F. Worboys Tripod: A Comprehensive Model for Spatial and Aspatial Historical Objects. 84-102 2001 conf/er/2001 ER http://link.springer.de/link/service/series/0558/bibs/2224/22240084.htm db/conf/er/er2001.html#GriffithsFPMHW01