Titan's fluvial valleys: Morphology, distribution, and spectral properties - Langhans, M.H.; Jaumann, R.; Stephan, K.; Brown, R.; Buratti, B.; Clark, Roger; Baines, K.; Nicholson, P.; Lorenz, R.; Soderblom, Laurence; Soderblom, J.M.; Sotin, Christophe; et al. (Planetary and Space Science, 2012)