@book{17993,
	author = {Bullen, K. E. and Bolt, Bruce A.,},
	title = {An introduction to the theory of seismology /},
	publisher = {Cambridge University Press,},
	year = {1985.},
	address = {Cambridge [Cambridgeshire] :},
	edition = {4th ed.},
	url = {http://www.loc.gov/catdir/description/cam022/84023052.html}
}