J stands for the Yahwist source, (Jahwist in German), and was considered to be the most primitive in style and therefore the oldest. E (for Elohist) was thought to be a product of the Northern Kingdom before BCE 721; D (for Deuteronomist) was said to be written shortly before it was found in BCE 621 by King Josiah . Old Testament scholar Karl Graf (1815–1869) suggested an additional priestly source in 1866; by 1878, Wellhausen had incorporated this source, P, into his theory, which is thereafter sometimes referred to as the Graf–Wellhausen hypothesis. Wellhausen argued that P had been composed during the exile, under the influence of Ezechiel. These sources are supposed to have been edited together by a late final Redactor (R) that is only imprecisely understood.