@article {1997,
	title = {Homogeneous tangent vectors and high order necessary conditions for optimal controls},
	journal = {J. Dynam. Control Systems 3 (1997), no. 2, 205--240},
	number = {SISSA;113/95/M},
	year = {1997},
	publisher = {SISSA Library},
	url = {http://hdl.handle.net/1963/1015},
	author = {Fabio Ancona}
}
