@article {,
	title = {Source of volcanic glass for ancient Andean tools},
	journal = {Nature},
	volume = {376},
	year = {1997},
	month = {April 3},
	pages = {449-450},
	keywords = {andes obsidian exchange source colca chivay},
	author = {Brooks, Sarah O. and Michael D. Glascock and Martin Giesso}
}