Two Roman Catholic bishops who led a central Pennsylvania diocese helped cover up the sexual abuse of hundreds of children by over 50 priests or religious leaders over a 40-year period. That’s according to a grand jury report issued today. The 147-page report on sexual abuse in the Altoona-Johnstown Diocese was based partly on evidence from a secret diocesan archive uncovered through a search warrant executed in August, said Pennsylvania Attorney General Kathleen Kane, who announced the findings. No criminal charges are being filed in the case because some abusers have died, the statute of limitations has expired and, in some cases, victims are too traumatized to testify, she said.  The report is especially critical of Bishops James Hogan and Joseph Adamec. Hogan, who headed the diocese from 1966 to 1986, died in 2005. Adamec, who succeeded him, retired in 2011.