Book of Order
Part II of the Constitution of the Presbyterian Church (U.S.A.).
The Constitution of the PC(U.S.A.) consists of several parts. The first volume is The Book of Confessions, the second (consisting of the Form of Government, Directory for Worship, and Rules of Discipline) is called the Book of Order.
The Book of Order contains the Form of Government, Directory for Worship, Rules of Discipline, and the Formula of Agreement. You may access the entire Book of Order in PDF format using the following links.
PC(USA) Constitution
http://www.pcusa.org/oga/constitution.htm