1917 M. A. Murray, “Statue of Nefer-Sma-Āa” in ed. Flinders Petrie, Ancient Egypt and the East, p.147:
The figure of the king wearing the Red Crown is uncommon when standing alone; it seldom occurs except in connection with a companion figure wearing the White Crown.
1931 Eric Peet, A Comparative Study of the Literatures of Egypt, Palestine and Mesopotamia: Egypt’s Contribution to the Literature of the Ancient World, p.64:
Two examples are here quoted, addressed respectively to the White Crown of Upper, and to the Red Crown of Lower Egypt: […] The Red Crown gleams upon thee, O Sobk, that thou mayest be protected.
2004 Michael Rice, Egypt’s Making: The Origins of Ancient Egypt 5000-2000 BC, p.112:
The earliest representation of the Red Crown, traditionally identified with the northern Kingdom is much earlier and is moulded on a pottery sherd recovered from a southern site, Naqada, and quite firmly dated to the Naqada I period, in the middle of the fourth millennium, c.3500 BC.