Gardiner, Alan Henderson (1957), Egyptian grammar being an introduction to the study of hieroglyphs, 3rd, revised edition, page 507
Seyr, Ph. (2023), Graphetic compounding in the First Intermediate Period: the micro-history of [hiero] ḥtr.wy "span" and the process of sign decomposition. Hieroglyphs 1, 149-183, p. 166, The sign at FIP Dendera.