[1] Albert R and Barabasi A L 2002 Rev. Mod. Phys. 74 47

[2] Boccaletti S et al %, Latora V, Moreno Y, Chavez M and Hwang D U
2006 Phys. Rep. 424 175

[3] Pastor-Satorras R and Vespignani A 2001 Phys. Rev. Lett.
86 3200

[4] Joo J and Lebowitz J L 2004 Phys. Rev. E 69 066105

[5] Barthelemy M and Barrat A 2005 J. Theor. Biol. 235 275

[6] Zheng D F et al %, Hui P M, Trimper S and Zheng B
2005 Physica A 352 659

[7] Liu Z, Lai Y C and Ye N 2003 Phys. Rev E 67 031911

[8] Naim E B 2004 Phys. Rev. E 69 050901

[9] Newman M E J 2002 Phys. Rev. E 66 016128

[10] Yan G et al %, Zhou T, Wang J, Fu Z Q and Wang B H
2005 Chin. Phys. Lett. 22 510

[11] Zhang H, Liu Z and Ma W 2006 Chin. Phys. Lett. 23 1050

[12] Eguiluz V M and Klemm K 2002 Phys. Rev. Lett. 89 108701

[13] Liu Z and Hu B 2005 Europhys. Lett. 72 315

[14] Crank J 1970 The Mathematics of Diffusion (Oxford: Clarendon)

[15] Metzler R et al %, Barkai E and Klafter J
1999 Phys. Rev. Lett. 82 3563

[16] Rangarajan G and Ding M 2000 Phys. Rev. E 62 120

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