Source clustering in the Hi-GAL survey determined using a minimum spanning tree method M. Beuret, N. Billot, L. Cambrésy, D. J. Eden, D. Elia, S. Molinari, S. Pezzuto and E. Schisano A&A, 597 (2017) A114 Published online: 12 January 2017 DOI: 10.1051/0004-6361/201629199