@inproceedings{SAC-1994-FlorianiMP,
	author        = "Leila De Floriani and Paola Marzano and Enrico Puppo",
	booktitle     = "{Proceedings of the Ninth Symposium on Applied Computing}",
	doi           = "10.1145/326619.326767",
	pages         = "323--327",
	publisher     = "{ACM}",
	title         = "{Hierarchical terrain models: survey and formalization}",
	year          = 1994,
}