with tables showing the position taken in most of the standard works before 2000. (Roelcke 1998) Roelcke T (1998). "Die Periodisierung der deutschen Sprachgeschichte". In Besch W, Betten A, Reichmann O, Sonderegger S (eds.). Sprachgeschichte (in German). Vol. 2 (2nd ed.). Berlin, New York: Walter De Gruyter. pp. 798–815. ISBN3-11-011257-4.
But see Fausto Cercignani (2022). The development of the Old High German umlauted vowels and the reflex of New High German /ɛ:/ in Present Standard German. Linguistik Online. 113/1: 45–57. Online