In some works the ogonek hook is not attached ◌᪷. Pullum & Ladusaw (1996:253) identified the diacritic as a left half ring ◌̜ "less rounded" diacritic but several references make it clear it is an ogonek. See Whitley 2003, p. 84. Whitley, M. Stanley (2003). "Rhotic representation: problems and proposals". Journal of the International Phonetic Association. 23 (1): 81–86. doi:10.1017/S0025100303001166. S2CID145538124.
MacMahon (1986), pp. 35, 38 n. 20. MacMahon, Michael K. C. (1986). "The International Phonetic Association: The first 100 years". Journal of the International Phonetic Association. 16 (1): 30–38. doi:10.1017/S002510030000308X. S2CID145576661.
Esling (2010), p. 681. Esling, John H. (2010). "Phonetic Notation". In Hardcastle, William J.; Laver, John; Gibbon, Fiona E. (eds.). The Handbook of Phonetic Sciences (2nd ed.). Wiley-Blackwell. pp. 678–702. doi:10.1002/9781444317251.ch18. ISBN978-1-4051-4590-9.
Esling (2010), pp. 681–2. Esling, John H. (2010). "Phonetic Notation". In Hardcastle, William J.; Laver, John; Gibbon, Fiona E. (eds.). The Handbook of Phonetic Sciences (2nd ed.). Wiley-Blackwell. pp. 678–702. doi:10.1002/9781444317251.ch18. ISBN978-1-4051-4590-9.
Esling (2010), p. 697. Esling, John H. (2010). "Phonetic Notation". In Hardcastle, William J.; Laver, John; Gibbon, Fiona E. (eds.). The Handbook of Phonetic Sciences (2nd ed.). Wiley-Blackwell. pp. 678–702. doi:10.1002/9781444317251.ch18. ISBN978-1-4051-4590-9.
To be precise, the shape of ⟨ǥ⟩ is close to ⟨⟩ in the 1900, 1904, and 1912 charts, and to ⟨⟩ in the 1921 chart and Jones (1928). Jones, Daniel (1928). "Das System der Association Phonétique Internationale (Weltlautschriftverein)". In Heepe, Martin (ed.). Lautzeichen und ihre Anwendung in verschiedenen Sprachgebieten. Berlin: Reichsdruckerei. pp. 18–27. Reprinted in Le Maître Phonétique 3, 6 (23), July–September 1928, JSTOR44704262. Reprinted in Collins & Mees (2003).
Association phonétique internationale (1904), p. 9, citing Sweet (1902), p. 37. Association phonétique internationale (1904). "Aim and Principles of the International Phonetic Association". Le Maître Phonétique. 19 (11). Supplement. JSTOR44703664. Sweet, Henry (1902). A Primer of Phonetics (2nd ed.). Oxford University Press.
Jones (1928), p. 26. Jones, Daniel (1928). "Das System der Association Phonétique Internationale (Weltlautschriftverein)". In Heepe, Martin (ed.). Lautzeichen und ihre Anwendung in verschiedenen Sprachgebieten. Berlin: Reichsdruckerei. pp. 18–27. Reprinted in Le Maître Phonétique 3, 6 (23), July–September 1928, JSTOR44704262. Reprinted in Collins & Mees (2003).
Jones & Camilli (1933), p. 11. Jones, Daniel; Camilli, Amerindo (1933). "Fondamenti di grafia fonetica secondo il sistema dell'Associazione fonetica internazionale". Le Maître Phonétique. Troisième série. 11 (43). Supplement. JSTOR44704558. Reprinted in Collins & Mees (2003).
Association phonétique internationale (1927). Association phonétique internationale (1927). "desizjɔ̃ dy kɔ̃sɛːj rəlativmɑ̃ o prɔpozisjɔ̃ d la kɔ̃ferɑ̃ːs də *kɔpnag" [Décisions du conseil relativement aux propositions de la conférence de Copenhague]. Le Maître Phonétique. Troisième série. 5 (18): 13–18. JSTOR44704201.
Jones (1928), pp. 23, 25–7. Jones, Daniel (1928). "Das System der Association Phonétique Internationale (Weltlautschriftverein)". In Heepe, Martin (ed.). Lautzeichen und ihre Anwendung in verschiedenen Sprachgebieten. Berlin: Reichsdruckerei. pp. 18–27. Reprinted in Le Maître Phonétique 3, 6 (23), July–September 1928, JSTOR44704262. Reprinted in Collins & Mees (2003).
In some works the ogonek hook is not attached ◌᪷. Pullum & Ladusaw (1996:253) identified the diacritic as a left half ring ◌̜ "less rounded" diacritic but several references make it clear it is an ogonek. See Whitley 2003, p. 84. Whitley, M. Stanley (2003). "Rhotic representation: problems and proposals". Journal of the International Phonetic Association. 23 (1): 81–86. doi:10.1017/S0025100303001166. S2CID145538124.
MacMahon (1986), pp. 35, 38 n. 20. MacMahon, Michael K. C. (1986). "The International Phonetic Association: The first 100 years". Journal of the International Phonetic Association. 16 (1): 30–38. doi:10.1017/S002510030000308X. S2CID145576661.
Wells (2006). Wells, John C. (6 November 2006). "Scenes from IPA history". John Wells's phonetic blog. Department of Phonetics and Linguistics, University College London.