Howard Zehr's book "Changing Lenses–A New Focus for Crime and Justice", first published in 1990, is credited with being "groundbreaking", as well as being one of the first to articulate a theory of restorative justice. The title of this book refers to providing an alternative framework for thinking about – or new lens for viewing – crime and justice. "Changing Lenses" juxtaposed a "retributive justice" framework, where crime is viewed as an offense against the state, with a restorative justice framework, where crime is viewed as a violation of people and relationships. The book made reference to the positive results of efforts in the late 1970s and 1980s at victim–offender mediation, pioneered in the United States by Howard Zehr, Ron Claassen and Mark Umbreit.