He is professor of New Testament Studies at the Complutense University of Madrid. He has taught in this university Coptic section Trilingual Biblical Philology. He is editor and co-author of the Old Testament Apocrypha series (6 vols., 1983) and Apocryphal Acts of the Apostles (with Gonzalo del Cerro) (2 vols., 2005). Among his studies on the New Testament stand The other Jesus. Life of Jesus according to the apocryphal gospels (1993) and The New Testament. Introduction to the study of early Christian writings (with J. Peláez) (1996, English 2003 ed.). He has edited and contributed to the following anthologies: Origins of Christianity. Background and first steps (1991), Sources of Christianity. Early traditions of Jesus (1994), On the frontier of the impossible. Magos, doctors and miracle workers in the eastern Mediterranean in time of the Bible (2001) Bible and Hellenism. Greek Thought and formation of Christianity (2006). In this same Editorial, is editor and co-author of Gnostic Texts. Nag Hammadi Library, in three volumes (I, 2000, II, 2004, III, 2000).