[1] Barab\'asi A-L and Albert R 1999 Science 286
p509

[2] Dorogovtsev S N and Mendes J F F 2001 Phys. Rev. E
63 025101

[3] Fortunato S, Flammini A and Menczer1 F 2006 Phys.
Rev. Lett. 96 218701

[4] Barab\'asi A-L, Albert R and Jeong H 1999 Physica A
272 173

[5] Krapivsky P L, Redner S and Leyvraz F 2000 Phys. Rev.
Lett. 85 4629

[6] Dorogovtsev S N, Mendes J F F and Samukhin A N 2000
Phys. Rev. Lett. 85 4633

[7] Bollob\'as B and Riordan O M 2002 Handbook of
Graphs and Networks ed Bornholdt S and Schuster H G (Berlin:
Wiley--VCH) chap 1 pp 1--34

[8] Bollob\'as B, Riordan O M, Spencer J and Tusn\'ady G 2001
Random Structures and Algorithms 18 279

[9] Holme P and Kim B J 2002 Phys. Rev. E 65
026107

[10] Hou Z T, Kong X X, Shi D H and Chen G R 2008 arXiv:
0805.1434v1 [math.PR] 9 May

[11] Shi D H, Chen Q H and Liu L M 2005 Phys. Rev. E
71 036140