BARBARA WHITE STACK has covered issues regarding abused, neglected and delinquent children for the Pittsburgh Post-Gazette for 12 years. She began work on this series of articles three years ago when she sent her first request under the state Right to Know law to the state Department of Public Welfare for information on children injured in DPW-licensed group homes in Allegheny County. Since then, Stack has filed a dozen Right to Know requests with DPW in attempts to get information on child injuries. Initially, DPW refused information sought in those requests and delayed responding. Recently, however, under the administration of DPW Secretary Estelle Richman, the department not only provided information but expedited responses.