Source criticism's most influential work is Julius Wellhausen's "Prolegomena zur Geschichte Israels" ("Prologue to the History of Israel", 1878) which sought to establish the sources of the first five books of the Old Testament collectively known as the Pentateuch. Wellhausen correlated the history and development of those five books with the development of the Jewish faith. The Wellhausen hypothesis, also known as the "JEDP" theory, or the Documentary hypothesis, or the Graf–Wellhausen hypothesis proposes that the Pentateuch was combined out of four separate and coherent (unified single) sources (not fragments).