[1] M. Nowak, D. Krakauer, Proc. Natl. Acad. Sci. USA 96 (1999) 8028.

[2] D. Abrams, S. Strogatz, Nature 424 (2003) 900.

[3] C. Schulze, D. Stauffer, Int. J. Mod. Phys. C 16 (2005) 718 and AIP Conference proceedings 119, 49 (2005) (8th Granada Seminar).

[4] C. Schulze, D. Stauffer, Phys. Life Rev. 2 (2005) 89.

[5] K. Kosmidis, J.M. Halley, P. Argyrakis, Physica A 353 (2005) 595.

[6] K. Kosmidis, A. Kalampokis, P. Argyrakis, Physica A, in press (physics/051019).

[7] J. Mira, A. Paredes, Europhys. Lett. 69 (2005) 1031.

[8] V. Schwammle, Int. J. Mod. Phys. C 16 (10) (2005) 1519 physics/ 0503238.

[9] V. Schwammle, Int. J. Mod. Phys. C 17 (3) 2006, physics/ 0509018.

[10] T. Tesileanu, H. Meyer-Ortmanns, Int. J. Mod. Phys. C 17 (3) (2006), physics/0508229.

[11] M. Patriarca, T. Leppapen, Physica A 338 (2004) 296.

[12] V.M. de Oliveira, et al., Physica A 361 (2006) 361.

[13] V.M. de Oliveira et al., Physica A, in press (physics/0510249).

[14] G.K. Zipf, Human Behavior and the Principle of Least Effort: An Introduction to Human Ecology, Addison-Wesley, Cambridge, MA, 1949.

[15] S. Havlin, Physica A 216 (1995) 148.

[16] R. Cancho, R. Sole, Proc. Natl. Acad. Sci. USA 100 (2003) 788.

[17] D.S.G. Pollock, Time series analysis, Signal Processes and Applications, Academic Press, London, 1999.

[18] C.-K. Peng, et al., Nature (London) 356 (1992) 168.

[19] R.F. Voss, Phys. Rev. Lett. 68 (1992) 3805.

[20] S.V. Buldyrev, et al., Phys. Rev. Lett. 71 (1993) 1776.

[21] A. Arneodo, E. Bacry, P.V. Graves, J.F. Muzy, Phys. Rev. Lett. 74 (1995) 3293.

[22] R.N. Mantegna, et al., Phys. Rev. Lett 73 (1994) 3169.

[23] S.V. Buldyrev, et al., in: A. Bunde, S. Havlin (Eds.), Fractals in Science, Springer, Berlin, 1994.

[24] E. Koscielny-Bunde, et al., Phys. Rev. Lett. 81 (1998) 729.

[25] C.-K. Peng, et al., Phys. Rev. Lett. 70 (1993) 1343.

[26] C.-K. Peng, et al., Chaos 5 (1995) 82.

[27] C.-K. Peng, et al., Physica (Amsterdam) 249A (1998) 491.

[28] S. Thurner, M.C. Feurstein, M.C. Teich, Phys. Rev.Lett. 80 (1998) 1544.

[29] L.A. Amaral, A.L. Goldberger, P. Ch. Ivanov, H.E. Stanley, Phys. Rev. Lett. 81 (1998) 2388.

[30] P.Ch. Ivanov, et al., Nature (London) 399 (1999) 461.

[31] C.K. Peng, et al., Phys. Rev. E 49 (2) (1994) 1685.

[32] J. Kantelhardt, E. Koscielny-Bunde, H. Rego, S. Havlin, A. Bunde, Physica A 295 (2001) 441.

[33] P. Grassberger, I. Procaccia, Phys. Rev. Lett. 50 (1983) 346.

[34] P. Grassberger, I. Procaccia, Physica D 9 (1983) 189.

[35] G. Nicolis, I. Prigogine, Exploring Complexity, Freeman, New York, 1989.

[36] C. Kotsavasiloglou, A. Kalampokis, P. Argyrakis, S. Baloyannis, Phys. Rev. E 56 (4) (1997) 4489.

[37] Ch. Karakotsou, A.N. Anagnostopoulos, Physica D 93 (1996) 157.

[38] Ch. L. Koliopanos, I.M. Kyprianidis, I.N. Stouboulos, A.N. Anagnostopoulos, L. Magafas, Chaos Soliton Fract 16 (2003) 173.

[39] A. Schenkel, J. Zhang, Y.-C. Zhang, Fractals 1 (1993) 47.

[40] R.F. Voss, Fractals 2 (1994) 1.

[41] M. Amit, Y. Shemerler, E. Eisenberg, M. Abraham, N. Shnerb, Fractals 2 (1) (1994) 7.

[42] M. Montemurro, P. Pury, Fractals 10 (4) (2002) 451.

[43] A. Bunde, J.F. Eichner, J.W. Kantelhardt, S. Havlin, Phys. Rev. Lett. 94 (2005) 048701.