@inproceedings{STOC-1969-Rounds,
	author        = "William C. Rounds",
	booktitle     = "{Proceedings of the First Annual ACM Symposium on Theory of Computing}",
	doi           = "10.1145/800169.805428",
	pages         = "143--148",
	publisher     = "{ACM}",
	title         = "{Context-Free Grammars on Trees}",
	year          = 1969,
}