@Article{ MaNoPlRi15, author = { Bruno Martelli and Matteo Novaga and Alessandra Pluda and Stefano Riolo }, title = { Spines of minimal length }, journal = { Ann. Sc. Norm. Super. Pisa Cl. Sci. }, year = { 2017 }, doi = { 10.2422/2036-2145.201511_003 }, volume = { XVII }, pages = { 1067-1090 }, }