@inproceedings{SIGMOD-1981-Johnson,
	author        = "Rowland R. Johnson",
	booktitle     = "{Proceedings of the 11th ACM SIGMOD International Conference on Management of Data}",
	cdrom         = "SIGMOD81/P093.PDF",
	doi           = "10.1145/582318.582333",
	pages         = "93--97",
	publisher     = "{ACM Press}",
	title         = "{Modelling Summary Data}",
	year          = 1981,
}