The second source, more closely interwoven in the narrative of Genesis-Numbers, and Joshua, has also such strongly marked peculiarities, not only in religious ideas and in phraseology and style, but in its whole conception and treatment of the history, that it stands out in salient contrast to any surroundings in which it may occur. Its interest is concentrated on the origin of the sacred institutions of Israel, especially on the priesthood, the worship, and the distinctive religious customs of the people, for which reason it is commonly called the "priestly" history and law. The two remaining sources resemble each other much more closely in religious conceptions, in language, and in their representation of the history, so that, where their closely parallel narratives are intimately interwoven to make one continuous and harmonious story, it is often impossible to unravel them. As far as Exod. iii. 14 one of them employs the name Elohim for God, while the other uses Jehovah from the beginning (see Gen. iv. 26), and this difference frequently serves as a first clue; but editors and copyists have so often, purposely or thoughtlessly, interchanged the names of God that it is by no means a decisive criterion. From Exod. 3 on, this criterion fails altogether. Closer acquaintance with the two sources discovers, under all their similarity, individual peculiarities by which they can ordinarily be recognized. Frequently, also, the connection of the story itself, references or allusions to incidents already recounted and preparation for events subsequently to be narrated, serve to identify passages with one or the other. For the sake of brevity, it is customary to designate these sources by symbols: J (Jahvist), the source in which God is from the beginning called Jehovah (more exactly, Jahveh); E (Elohist), the closely cognate source in which Elohim (God) is consistently used throughout Genesis; D, Deuteronomy and the kindred narrative in Joshua; P (Priestly), the source in which the interest in the religious institutions predominates. This author also uses Elohim exclusively in Genesis, and down to Exod. vi. 2 ff.