@conference {105,
	title = {Ultrasonic Sensor System for Detecting Falling Objects on Railways},
	booktitle = {IEEE Intelligent Vehicles Symposium (IV{\textquoteright}04)},
	volume = {1},
	year = {2004},
	month = {06/2004},
	pages = {866 - 871},
	address = {Parma, Italia},
	isbn = {0-7803-8311-7},
	attachments = {https://smtp.geintra-uah.org/system/files/private/IV04_II.pdf},
	author = {Fernando J. {\'A}lvarez and Ure{\~n}a, J. and Manuel Mazo and {\'A}lvaro Hern{\'a}ndez and J.J. Garcia and Patricio Gabriel Donato}
}
