The use of the sound [ç] after front vowels is supported by developments in English pronunciation seen from the thirteenth century onward: original /x/ sometimes became /f/ after a back vowel (e.g. rough, tough, trough), but this change is never seen after a front vowel. That is explained if the allophone [x] sometimes became [f], but the allophone [ç] never did so.[44]Lass 1994 considers it uncertain that [ç] was used already in Old English, whereas Hogg 1992 regards it as certain that ⟨h⟩ had developed a palatal version, like other velar consonants.[41] Lass, Roger (1994). Old English: A historical linguistic companion. Cambridge: Cambridge University Press. ISBN0-521-43087-9. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, p. 68. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Minkova 2011, pp. 33–34. Minkova, Donka (2011). "Phonemically Contrastive Fricatives in Old English?". English Language and Linguistics. 15 (1). Cambridge University Press: 31–59. doi:10.1017/S1360674310000274.
Fulk 2002, pp. 83, 94. Fulk, R. D. (2002). "Conditions for the voicing of Old English fricatives, II: morphology and syllable structure". English Language and Linguistics. 6 (1): 81–104. doi:10.1017/S1360674302001053.
Hogg 1992, pp. 108–111. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, p. 109. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, p. 92. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Fulk 2002, pp. 84–85. Fulk, R. D. (2002). "Conditions for the voicing of Old English fricatives, II: morphology and syllable structure". English Language and Linguistics. 6 (1): 81–104. doi:10.1017/S1360674302001053.
Fulk 2002, pp. 93–95. Fulk, R. D. (2002). "Conditions for the voicing of Old English fricatives, II: morphology and syllable structure". English Language and Linguistics. 6 (1): 81–104. doi:10.1017/S1360674302001053.
Hogg 1992, p. 107. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Fulk 2002, p. 97. Fulk, R. D. (2002). "Conditions for the voicing of Old English fricatives, II: morphology and syllable structure". English Language and Linguistics. 6 (1): 81–104. doi:10.1017/S1360674302001053.
Hogg 1992, p. 93. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, p. 94. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 92–94. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 85–86 Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 119–122. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 88, 120. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, p. 86. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 86–87, 101. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 86–87. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, p. 96. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Toon 1992, p. 429. Toon, Thomas E. (1992). "Chapter 6: Old English Dialects". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 101–105. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, p. 112. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 98–100. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Fulk 2002, pp. 82–83. Fulk, R. D. (2002). "Conditions for the voicing of Old English fricatives, II: morphology and syllable structure". English Language and Linguistics. 6 (1): 81–104. doi:10.1017/S1360674302001053.
Hogg 1992, pp. 96–98. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Hogg 1992, pp. 94, 98. Hogg, Richard M. (1992). "Chapter 3: Phonology and Morphology". In Hogg, Richard M. (ed.). The Cambridge History of the English Language. Vol. 1: The Beginnings to 1066. Cambridge University Press. pp. 67–168. doi:10.1017/CHOL9780521264747. ISBN978-0-521-26474-7.
Colman 2004, pp. 174–174. Colman, Fran (2004). "Kentish Old English <b>/<B>: orthographic 'archaism' or evidence of Kentish phonology?". English Language and Linguistics. 8 (2): 171–205. doi:10.1017/S1360674304001364.