Gaudium et Spes" is also known as The Pastoral Consitution on the Church in the Modern World.  Norman Tanner, S.J. is a professor of church history at the Gregorian University in Rome.  In this book he traces the document's evolution into what emerged as the most distinctive and challenging decree of the Vatican Council.  Unlike any coucil document before or after it, this decree was uniquely and deliberately addressed to the world at large stating what the council fathers hoped the church to be.  [Paulist Press, 2005]