@book{75869,
	author = {Lenzen, Victor F. and Multhauf, Robert P.,},
	title = {Development of Gravity Pendulums in the 19th Century :},
	publisher = {Project Gutenberg,},
	year = {2011},
	address = {Salt Lake City, UT :},
	note = {Release date is 2011-01-21},
	url = {https://www.gutenberg.org/ebooks/35024}
}