@book{50818,
	author = {Baring-Gould, S.},
	title = {Cliff Castles and Cave Dwellings of Europe},
	publisher = {Project Gutenberg,},
	year = {2005},
	address = {Salt Lake City, UT :},
	note = {Release date is 2005-09-01},
	url = {https://www.gutenberg.org/ebooks/8898}
}