[1] Barab\'{asi A L and Albert R 1999 Science
286 509

[2] Biley N T J 1975 The Mathematical Theory of
Infectious Diseases and its Applications 2nd edn (London: Griffin)

[3] Pastor-Satorras R and Vespignani A 2001 Phys. Rev. E
63 066117

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

[5] Warren C P, Sander L M and Sokolov I M 2003 Physica
A 325 1

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

[7] Barth\'{elemy M, Barrat A, Pastor-Satorras R and
Vespignani A 2004 Phys. Rev. Lett. 92 178101

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

[9] Zhou T, Liu J G, Bai W J, Chen G and Wang B H 2006
Phys. Rev. E 74 056109

[10] Li X and Wang X F 2006 IEEE Trans. Autom. Control
51 534

[11] Colizza V, Barrat A, Barth\'{ememy M and Vespignani A
2006 Proc. Natl. Acad. Sci. USA 103 2015

[12] Xu X J, Zhang X and Mendes J F F 2007 Phys. Rev. E
76 056109

[13] Altmann M 1995 J. Math. Biol. 33 661

[14] Gross T, Dommar D'Lima C J and Blasius B 2006 Phys.
Rev. Lett. 96 208701

[15] Liu Z R, Yan J R, Zhang J G and Wang L 2006 Chin.
Phys. Lett. 23 1343