LIST OF CORRECTIONS FOR 1st and 2nd printing Please accept my sincere apologies for this series of misprints. I am working to produce a pdf file of the size of the book page to be attached at the end of the text with the relevant information. Here you can find the list (at the moment)

• page xii, line 6 602,300,000 --> 602,214,179
• page 3, line 28 Yahoo --> Yahoo!
• page 113, line 7 (acknowledgements to M.W. Fontana)
  ..with a disconnected set of n_0 vertices (no edges are present) -->
  with a set of m_0 vertices with at least degree 1
• page 113, line 16 n_0 --> >m_0
• page 113, line 23 n_0 --> >m_0
• page 203, line 19 N=AK^{-1} --> N=K^{-1}A
• page 203, line 20 ... are the degrees of vertices i --> ..are the out-degrees of vertices i
• page 212, footnote 68 A. Capocci, R. Ferrer i Cancho, G. Caldarelli --> R. Ferrer i Cancho, A. Capocci, G. Caldarelli
• page 283 lines 23-24 Remove Amaral and Barthelemy in Bibliography
  pag.111 line 14 (Amaral and Barthelemy, 1999) --> (Barth\'elemy and Amaral, 1999a)
• page 283, line 9 Ahnert et al. arXiv.org:cond-mat/0604409 ---> Physical Review E 76, 016101 (2007)
• page 285 lines 23-24 Bollen et al. arXiv.org.cs--> 669-687 (2006)
• page 288 lines 12-15 Chen et al. XXX, arXiv.org:physics/0604130 --> 8-15 (2007).
• page 289 lines 29-38 In the papers by Dodds and Rothman the letter i, ii, iii in the titles must be capitalised
i.e. Geometry of river networks. i ---> Geometry of river networks. I.
• page 294 lines 6-8 Holloway et al. arXiV.... --> Complexity, 1, 30-40 (2007).