Collombert, Philippe (2010), Le tombeau de Mérérouka: paléographie. Paléographie hiéroglyphique 4, p. 10-11, §9
Fischer, Henry G. (1977), The evolution of composite hieroglyphs in ancient Egypt. Metropolitan Museum Journal 12, 5-19, p. 9
Pantalacci, Laure (2005), Nouveautés graphiques et lexicales dans le corpus des textes de Balat. In Seidlmayer, Stephan Johannes (ed.), Texte und Denkmäler des ägyptischen Alten Reiches, 275-285, p. 220, Cursive equivalent of the sign in the Letters from Balat.
Stauder, A. (2023), For the eye only: aspects of the visual text in ancient Egypt. In Zsolnay, Ilona (ed.), Seen not heard: composition, iconicity, and the classifier systems of logosyllabic scripts, 63-87, p. 65
Fischer, H.G. (1966), An Old Kingdom monogram: [sign] . Zeitschrift für ägyptische Sprache und Altertumskunde 93, 56-69., p. 68-69, Fischer discusses the use of the sign in Old Kingdom titles.