Borghouts, J. F. (2010), Egyptian: an introduction to the writing and language of the Middle Kingdom, 2 vols. Egyptologische Uitgaven 24, page 21, note 2
Fischer, Henry George (1996), Egyptian Studies III, Varia Nova, p. 177-179, On the general evolution of the grapheme.
Gardiner, Alan Henderson (1957), Egyptian grammar being an introduction to the study of hieroglyphs, 3rd, revised edition, page 447
Griffith, F. Ll. (1898), A collection of hieroglyphs: a contribution to the history of Egyptian writing. Archaeological Survey of Egypt 6, p. 13-14
Ogdon, J.R. (2004), Return to Coffin Texts spell 836 and the Hirtengeschichte. Cahiers caribéens d'égyptologie 6, 117-135, p. 123-131, On the identification of the herdsman and his staff.