@inproceedings{PODS-1989-RamakrishnanSUV,
	author        = "Raghu Ramakrishnan and Yehoshua Sagiv and Jeffrey D. Ullman and Moshe Y. Vardi",
	booktitle     = "{Proceedings of the Eighth Symposium on Principles of Database Systems}",
	cdrom         = "['journals/anthology/cd1-3:PODS89/P172.PDF', 'journals/anthology/dvd1:text/1-3/PODS89/P172.PDF']",
	doi           = "10.1145/73721.73739",
	isbn          = "0-89791-308-6",
	pages         = "172--181",
	publisher     = "{ACM Press}",
	title         = "{Proof-Tree Transformation Theorems and Their Applications}",
	year          = 1989,
}