Glendon Associates in Santa Barbara has many of the important research documents on suicide prevention and means restriction available as PDF documents and ready for download.
Click here for the link.
In addition the following references are most relevant:
On Restricting Access to Lethal Means
Mann, J.J.; Apter, A.; Bertolote, J.; Beautrais, A.; Currier. D.; Haas. A.; Heger, L.U.; Lonnqvist, J.; Malone, K.; Marusic, A.; Mehlum, L.; Patton, G.; Phillips, M.; Rutz, W.; Rihmer, Z.; Schmidtke, A.; Shaffer, D.; Silverman, M.; Takahashi, Y.; Varnik, A.; Wasserman, D.; Yip, P.; Hendin, H.: "Suicide prevention strategies: a systematic review". Journal of the American Medical Association, 2005; 294:2064–2074
Kreitman, N: "The coal gas story: United Kingdom suicide rates", 1960–71. British Journal of Preventative Social Medicine, 1976; 30:86–93
Gunnell, D.; Fernando, R.; Hewagama, M.; Priyangika, W.D.; Konradsen, F.; Eddlesston, M.: "The impact of pesticide regulations on suicide in Sri Lanka". International Journal of Epidemiology. 2007, 36:1235–1242
And With Regard to Bridges:
Reisch, T.; Michel, K.: "Securing a suicide hot spot: effects of a safety net at the Bern Muenster Terrace". Journal of Suicide and Life Threatening Behavior, 2005, 35:460–467
Bennewith O, Nowers M, Gunnell D: "Effect of barriers on the Clifton Suspension Bridge, England, on local patterns of suicide: implications for prevention". British Journal of Psychiatry, 2007, 190:266–267
Pelletier, Andrew R.: "Preventing suicide by jumping: the effect of a bridge safety fence." Injury Prevention, 2007, 13:57-59
Beautrais AL: "Effectiveness of barriers at suicide jumping sites: a case study." Australia and New Zealand Journal of Psychiatry. 2001, 35:557–562
Reisch, T.; Schusster, U.; Michel, K.: "Suicide by jumping and accessibility of bridges: results from a national survey in Switzerland." Journal of Suicide and Life Threatening Behavior, 2007, 37:681–687
Seiden, R.H.: "Where are they now? a follow-up study of suicide attempters from the Golden Gate Bridge." Journal of Suicide and Life Threatening Behavior, 1978, 8:203–216