Please find enclosed some references regarding the above subject.

Bandy, W.D., Irion, J.M., and Briggler, M. (1997) The effect of time and frequency of static stretching on flexibility of the hamstring muscles. Physical Therapy, 77(10), 1090-1096.

Bandy, W.D., Irion, J.M., and Briggler, M. (1998) The effect of static stretch and dynamic range of motion training on the flexibility of the hamstring muscles. The Journal of Orthopaedic and Sports Physical Therapy, 27 (4), 295-300.

Brandon, R. (1998) What science has to say about the performance benefits of flexibility training. Peak Performance, 108, 6-9.

Brodowicz, G.R., Welsh, R., and Wallis, M.S. (1996) Comparison of stretching with ice, stretching with heat, or stretching alone on hamstring flexibility. Journal of Athletic Training, 31(4), 324-327.

Gleim, G.W., and McHugh, M.P. (1997) Flexibility and its effects on sports injury and performance. Sports Medicine, 24(5), 289-299.

Kamper-Wevers, L., and O’Farrell, J. (1999) Gymnastic injuries. The way forward for elite gymnasts. Physiotherapy in Sport, 22(1), 4-10.

Magnusson, S.P., Simonsen, E.B., Aagaard, P., Boesen, J., Johannsen, F., Kjaer, M. (1997) Determinants of musculoskeletal flexiblity: Viscoelastic properties, cross sectional area, EMG and stretch tolerance. Scandinavian Journal of Medicine and Science in Sport, 7, 195-202.

McNair, P.J., and Stanley, S.N. (1996) Effect of passive stretching and jogging on the series elastic muscle stiffness and range of motion of the ankle joint. British Journal of Sports Medicine, 30, 313-318.

Stewart, I.B., and Sleivert, G.G. (1998) The effect of warm-up and intensity on range of motion and anaerobic performance. The Journal of Orthopaedic and Sports Physical Therapy, 27(2), 154-161.

Zito, M., Driver, D., Parker, C., and Bohannon, R. (1997) Lasting effects of one bout of two fifteen second passive stretches on ankle dorsiflexion range of motion. The Journal of Orthopaedic and Sports Physical Therapy, 26(4), 214-221.

I hope this is the sort of thing you are looking for.