Federal investigators hope the release of a threatening letter from the Army of God will help solve three bombings at an abortion clinic, a gay club and last summer Olympic Games in Atlanta. Almost a year after the bomb killed one person and injured more than a hundred at Centennial Olympic Park on July 27, officials said yesterday they’re increasingly certain the attack is related to later bombings at the Atlanta abortion clinic and the gay and lesbian night club. Investigators released detailed composite sketches of two men believed to have been seen outside the abortion clinic, along with a new photo showing a hazy figure sitting on the Olympic Park bench where that bomb was placed.