Walsem, René van (2020), Reinterpreting Gardiner, Egyptian Grammar, Sign-List N 5: : "ra": 'sun'. In Weber, Anke, Martina Grünhagen, Lea Rees, and Jan Moje (eds), Akhet neheh: studies in honour of Willem Hovestreydt on occasion of his 75th birthday,, page 14
Gardiner, Alan Henderson (1957), Egyptian grammar being an introduction to the study of hieroglyphs, 3rd, revised edition, page 485