The articles below are all by Doug Long, who has been studying the bombings since 1985. His website http://www.doug-long.com/ is a good source of links to further information.
The 'Was it necessary' articles below summarize the events that led to Japan's surrender in World War II and then consider other means of achieving Japan's surrender.
The 'Random ramblings' article addresses further subjects and issues on the topic of Hiroshima.
Clickon the link below to read an undergraduate essay on whether the bombing of Hiroshima was right or wrong.
This article from The Journal of Historical Review, May-June 1997 (Vol. 16, No. 3), pages 4-11, discusses the question of whether Hiroshima was necessary.