Kleineberg, Kaj-Kolja http://orcid.org/0000-0003-2944-5671
Boguñá, Marián http://orcid.org/0000-0001-7833-3487
Ángeles Serrano, M.
Papadopoulos, Fragkiskos http://orcid.org/0000-0002-4072-5781
Article History
Received: 20 January 2016
Accepted: 3 June 2016
First Online: 4 July 2016
Competing interests
: The authors declare no competing financial interests.