@inbook {BP97,
	title = {On some structural properties of general manipulation systems},
	booktitle = {Modelling and Control of Mechanichal Systems},
	year = {1997},
	pages = {187-202},
	publisher = {Imperial College Press},
	organization = {Imperial College Press},
	address = {London, U.K.},
	keywords = {Haptics, Robotics},
	author = {A. Bicchi and D Prattichizzo},
	editor = {A. Astolfi and D. J. N. Limebeer and C. Melchiorri and A. Tornamb\&egrave;e and R.B. Vinter}
}
