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Obsolete and nonstandard symbols in the International Phonetic Alphabet

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The International Phonetic Alphabet (IPA) possesses a variety of obsolete and nonstandard symbols. Throughout the history of the IPA, characters representing phonetic values have been modified or completely replaced. An example is ⟨ɷ⟩ for standard [ʊ]. Several symbols indicating secondary articulation have been dropped altogether, with the idea that they should be indicated with diacritics: ʮ for z̩ʷ is one. In addition, the rare voiceless implosive series ƥ ƭ 𝼉 ƈ ƙ ʠ has been dropped.

Other characters have been added in for specific phonemes which do not possess a specific symbol in the IPA. Those studying modern Chinese phonology have used ⟨ɿ⟩ to represent the sound of -i in Pinyin hanzi which has been variously described as [ɨ], [ɹ̩], [z̩] or [ɯ]. (See the sections Vowels and Syllabic consonants of the article Standard Chinese phonology.)

There are also unsupported symbols from local traditions that find their way into publications that otherwise use the standard IPA. This is especially common with affricates such as ƛ, and many Americanist symbols.

While the IPA does not itself have a set of capital letters (the ones that look like capitals are actually small capitals), many languages have adopted symbols from the IPA as part of their orthographies, and in such cases they have invented capital variants of these. This is especially common in Africa. An example is Kabiyé of northern Togo, which has Ɔ Ɛ Ŋ Ɣ. Other pseudo-IPA capitals supported by Unicode are Ɓ/Ƃ Ƈ Ɗ/Ƌ Ə/Ǝ Ɠ Ħ Ɯ Ɲ Ɵ Ʃ (capital ʃ) Ʈ Ʊ Ʋ Ʒ. (See Case variants of IPA letters.)

Capital letters are also used as cover symbols in phonotactic descriptions: C=Consonant, V=Vowel, N=Nasal, S=Sonorant, etc.

This list does not include commonplace extensions of the IPA, such as doubling a symbol for a greater degree of a feature ([aːː] extra-long [a], [ˈˈa] extra stress, [kʰʰ] strongly aspirated [k], and [a˞˞] extra-rhotic [a][1]), nor superscripting for a lesser degree of a feature ([ᵑɡ] slightly prenasalized [ɡ], [ᵗs] slightly affricated [s], and [ᵊ] epenthetic schwa). The asterisk, as in [k*] for the fortis stop of Korean, is the convention the IPA uses when it has no symbol for a phone or feature.

For symbols and values which were discarded by 1932, see History of the International Phonetic Alphabet.

Obsolete and/or nonstandard symbols in the International Phonetic Alphabet
Symbol or
exemplar
Name Meaning Standard IPA
equivalent
Notes
? question mark glottal stop ʔ typewriter substitution
7 digit seven glottal stop ʔ typewriter substitution
' apostrophe glottal stop ʔ typewriter substitution
q q glottal stop ʔ used in Maltese, Khmer and Malayo–Polynesian languages transcriptions.
ɋ q with hook bilabial click ʘ
φ Greek phi voiceless bilabial fricative ɸ a mistake, typewriter substitution or similarity of shape
ψ Greek psi retroflex click 𝼊, ‪‼ used by (Doke 1925)
bunched-r ɹ̈ proposed by John Laver (1994)
ß sharp s voiced bilabial fricative β a mistake, typewriter substitution or similarity of shape
,
or
integral symbol voiceless postalveolar fricative ʃ a mistake, typewriter substitution or similarity of shape
3 digit three voiced postalveolar fricative ʒ a mistake, typewriter substitution or similarity of shape; often confused with open-mid central unrounded vowel
đ d with stroke voiced dental fricative ð a mistake, typewriter substitution or similarity of shape
þ thorn voiceless dental fricative θ a mistake
ƍ turned delta labialized voiced alveolar or dental fricative zʷ, z͎, ðʷ intended for the voiced whistled sibilant, ɀ, of Shona and related languages, withdrawn 1976[2]
σ sigma labialized voiceless alveolar or dental fricative sʷ, s͎, θʷ intended for the voiceless whistled sibilant, ȿ, of Shona and related languages, withdrawn 1976[2]
ƺ ezh with tail labialized voiced alveolo-palatal fricative ʑʷ, ʒᶣ intended for w before front vowels in Twi;[2] may also be used for the lightly rounded English /ʒ/, withdrawn 1976.
ƪ reversed esh with top loop labialized voiceless alveolo-palatal fricative ɕʷ, ʃᶣ intended for hw before front vowels in Twi;[2] may also be used for the lightly rounded English /ʃ/, withdrawn 1976.
ƻ barred digit two voiced alveolar affricate d͡z withdrawn 1976
ƾ or ʢ turned voiced epiglottal trill voiceless alveolar affricate t͡s withdrawn 1976
ƞ eta moraic nasal m, n, ŋ, ɴ̩ Intended for the moraic nasal /N/ of Japanese.[2] Withdrawn 1976
◌̡ ( 𝼓 𝼔 𝼕 𝼖 ƫ 𝼘) palatal hook palatalization ɡ̟ ɬʲ ŋ̟ ɹʲ ɾʲ ɕ ʑ Typically used in the transcription of Slavic languages such as Russian. Superseded 1989
◌̢ retroflex hook voiced alveolar or retroflex approximant ɹ / ɻ a mistake; an example like // was actually [ʒ͡ɻ]
◌̢ retroflex hook r-colored vowels ɝ, ɚ or ɜ˞, ə˞ Superseded 1989; MODIFIER LETTER RHOTIC HOOK (U+02DE) is now preferred
unstressed central rhotic vowel r-colored vowel in American English ɝ, ɚ or ɜ˞, ə˞ Proposed in 1934, MODIFIER LETTER RHOTIC HOOK (U+02DE) is now preferred
ʃ ʒ t͡ʃ d͡ʒ alveolo-palatal consonants ɕ, ʑ, t͡ɕ, and d͡ʑ; respectively broad transcription; especially Japanologists and Koreanists
a a any open vowel Often a substitute for ɑ in printing when the distinction between a and ɑ is not needed.
ɑ Latin alpha any open vowel Often a substitute for ɑ in printing when the distinction between a and ɑ is not needed.
a reversed a near-open front unrounded vowel æ Proposed in 1989, rejected[3]
c c t͡ʃ, t͡ɕ or sometimes t͡s. broad transcription
nv ligature close front rounded vowel y proposed in 1989, rejected[3]
ᵿ˞ barred horseshoe u with hook back sulcal vowel proposed in 1989, rejected[3]
w with left hook voiced labial-velar fricative (labialized voiced velar fricative) ɣʷ proposed in 1989, rejected[3]
𝼥 𝼦 𝼧 𝼨 𝼩 𝼪 letters with left-swinging top hook dental consonants proposed in 1989, rejected;[3] Malayalam transcriptions
long-leg g voiced velar lateral approximant ʟ proposed in 1989, rejected[3]
hooktop ezh voiced velar fricative ɣ proposed in 1989, rejected[3]
double-loop g voiced velar fricative ɣ from 1895 to 1900, [q] represented that consonant before 1895, [ǥ] after 1900
double-loop g voiced velar plosive ɡ standard Unicode Basic Latin/ASCII lower-case g (U+0067) may have a double-loop g glyph. the preferred IPA single-loop g (U+0261) is in the IPA Extensions Unicode block. for a time it was proposed that the double-loop g might be used for [ɡ] and the single-loop g for [ᶃ] (ɡ̟),[2] but the distinction never caught on.
double-loop g voiced postalveolar affricate d͡ʒ used in Arabic transcriptions
single-loop g with stroke voiced velar fricative ɣ replaced double-loop g in 1900, then replaced by gamma [ɣ] around 1928-1930. the character ǥ may not have the single-loop shape in some fonts.
j j d͡ʒ, d͡ʑ or sometimes d͡z
ɟ barred dotless small j (or turned f in some fonts) d͡ʒ or d͡ʑ
ɡ̫ ʒ̫ etc. subscript w labialization ɡʷ ʍ ʒʷ ɥʷ etc. mark may appear above letters with descenders like [ɡ] or [ŋ]. removed 1989
ʆ curly-tail esh voiceless alveolo-palatal fricative ɕ variant, also for Russian щ (now ⟨ɕ⟩). removed 1989
ʓ curly-tail ezh voiced alveolo-palatal fricative ʑ variant, removed 1989
ȵ, ȡ, ȶ, ȴ curly-tail n, d, t, l alveolo-palatal consonants n̠ʲ, d̠ʲ, t̠ʲ, l̠ʲ or ɲ̟, ɟ˖, c̟, ʎ̟ used by some Sinologists.
ř r with háček voiced strident apico-alveolar trill Intended for ř in Czech and related languages. ⟨ř⟩ from 1909, replaced by ⟨ɼ⟩ in 1949, Withdrawn 1989
ɼ long-leg r voiced strident apico-alveolar trill Intended for ř in Czech and related languages. ⟨ř⟩ from 1909, withdrawn 1989.
ɼ long-leg r syllabic alveolar trill a mistake
λ () Greek lambda voiced palatal lateral approximant ʎ a mistake
voiced alveolar lateral affricate d͡ɮ used by Americanists
ƛ barred lambda voiceless alveolar lateral affricate t͡ɬ used by Americanists
ł l with stroke voiceless alveolar lateral fricative ɬ used by Americanists, also a typographic substitute
ł l with stroke velarized voiced alveolar lateral approximant ɫ used by Baltic transcriptions
small capital Cyrillic el voiced uvular lateral approximant ʟ̠
š č ž s c z with háček postalveolar consonants ʃ t͡ʃ ʒ; ʂ ʈ͡ʂ ʐ used by Americanists, Uralicists, Semiticists, Slavicists
ǰ, ǧ, ǯ j, g, ezh with háček voiced postalveolar affricate d͡ʒ; ɖ͡ʐ used by Americanists, Slavicists
ć ĺ ń ś ź c l n s z dz with acute accent alveolo-palatals or palatals and postalveolar consonants t͡ɕ l̠ʲ n̠ʲ ɕ ʑ d͡ʑ; t͡ʃ ʎ ɲ ʃ ʒ d͡ʒ used by Slavicists
x, ɣ x, Latin gamma voiceless and voiced uvular fricative (or voiced uvular approximant) χ, ʁ or χ, ʁ̞ broad transcriptions in Hindi, Arabic and Hebrew transcriptions
x with dot voiceless uvular fricative χ used by Americanists
X uppercase x voiceless uvular fricative χ a mistake
Y uppercase y voiced labial–palatal approximant ɥ a mistake
baby gamma close-mid back unrounded vowel ɤ used from 1921 to 1989, replaced by ramshorn to avoid confusion with gamma ; LATIN SMALL LETTER RAMS HORN (U+0264) now represents both glyphs
ρ rho bilabial trill ʙ common before an official letter was adopted
ɉ barred j voiced post-palatal approximant ȷ̈
ɥ̵ barred turned h compressed voiced post-palatal approximant ɥ̈
barred w protruded voiced post-palatal approximant
/ ᵿ barred small capital i / upsilon near-close central unrounded / rounded vowel ɪ̈ / ʊ̈, ɨ̞ / ʉ̞, ɘ̝ / ɵ̝, ɪ̠ / ʊ̟ used by some English phoneticians, including the Oxford English Dictionary
ʚ closed epsilon open-mid front rounded vowel œ alternate symbol from 1904-1920s[4]
ʚ closed epsilon open-mid central rounded vowel ɞ removed 1996
ɩ Latin iota near-close near-front unrounded vowel ɪ longstanding alternate symbol until 1989
barred Latin iota near-close central unrounded vowel ɪ̈, ɨ̞, ɘ̝, ɪ̠ longstanding alternate symbol until 1989
ı dotless small i near-close near-front unrounded vowel ɪ a mistake or typographic substitute; or used by Americanists.
ȸ ȹ db and qp ligatures or footless phi and headless phi voiced and voiceless labiodential plosives Used by Africanists.
0, , or Ø digit zero, slashed digit zero or uppercase slashed o null initial usually used in phonology to mean a spelling with no sound value. however, in Chinese and some Korean linguistics, some scholars use it for a weak glottal stop; the sound value of the first consonant of syllables started by a vowel.
ƥ ƭ 𝼉 ƈ ƙ ʠ hooktop p, t, ʈ, c, k, q voiceless implosives ɓ̥ ɗ̥ ᶑ̊ ʄ̊ ɠ̊ ʛ̥ or pʼ↓ tʼ↓ ʈʼ↓ cʼ↓ kʼ↓ qʼ↓ brief additions to the IPA; removed 1993
ʇ turned t dental click ǀ removed 1989; see click letters
ʗ stretched (or descended) c alveolar click ǃ removed 1989; see click letters
ʖ turned pharyngeal fricative alveolar lateral click ǁ removed 1989; see click letters
ʞ turned k originally a palatal click, reinterpreted as a velar click velar articulation was judged impossible.[5] later reanalyzed and found paralinguistically. For several years used for a voiceless velodorsal stop in the extIPA.[6]
𝼋 (⨎) esh with two bars fricated palatal click ǂǂ or ǃ͡s uncommon letter in Ekoka !Kung transcription
triple vertical bar retroflex lateral click ǁ˞
ȣ ou close-mid back unrounded vowel or voiced velar fricative ɤ or ɣ a common mistake
r r alveolar trill any rhotic sound (including r-colored vowels) broad transcription
ʀ or R small capital or uppercase r long vowel or prolonged moraic N ː used by Japanologists. This symbol represents phonemic long vowel (such as //) or /aR/) or rarely prolonged moraic N (hatsuon).
reversed small capital r voiced epiglottal trill[citation needed] ʢ or ʀ̠ rare
ɿ dotless long i with fishhook syllabic denti-alveolar approximant ɹ̩,[7] ɹ̩, z̩, ◌͡ɯ[8] used by Sinologists, and by Japanologists specifically for the Miyako and Tarama languages.
ʅ dotless long i with fishhook and tail syllabic retroflex approximant ɹ̩,[7] ɻ̩, ʐ̩, ◌͡ɨ used by Sinologists. See Chinese vowels
ʮ turned h with fishhook labialized syllabic denti-alveolar approximant ɹ̩ʷ, z̩ʷ, ◌͡u used by Sinologists
ʯ turned h with fishhook and tail labialized syllabic retroflex approximant ɻ̩ʷ, ʐ̩ʷ, ◌͡ʉ used by Sinologists
small capital a open central unrounded vowel ä, ɑ̈, ɐ̞, a̠, ɑ̟ used by Sinologists
small capital turned a close-mid back unrounded vowel ɤ withdrawn in 1928.
barred Latin alpha open central unrounded vowel ä, ɑ̈, ɐ̞, a̠, ɑ̟ Proposed by Charles-James N. Bailey in 1976[9]
small capital e mid front unrounded vowel e̞, ɛ̝ Bloch & Trager (1942). Used by Sinologists and some Koreanists
barred e close-mid central unrounded vowel ɘ used by Teuthonista
small capital turned e mid back unrounded vowel ɤ̞, ʌ̝ used by some Koreanists who study Gyeongsang dialect, where there is no phonemic differentiation between /ʌ/ (RR eo; Hangul ㅓ) and /ɯ/ (RR eu; Hangul ㅡ).[citation needed]
ɷ closed omega near-close near-back rounded vowel ʊ longstanding alternate symbol until 1989
ω omega near-close near-back unrounded vowel ɯ̽ or ʊ̜ made from obsolete ɷ symbol.
ω omega near-open back rounded vowel ɒ̝, ɔ̞ used by Sinologists ; also Bloch & Trager (1942).
small capital omega mid back rounded vowel o̞, ɔ̝ Used by Sinologists and some Koreanists ; also Bloch & Trager (1942).
barred o close-mid central rounded vowel ɵ used by Teuthonista
small capital u near-close near-back rounded vowel ʊ Americanist notation
barred small capital u near-close central rounded vowel ʊ̈, ʉ̞, ɵ̝, ʊ̟ Americanist notation
B G Ɠ H I L N Œ R Y uppercase letters small caps ʙ ɢ ʛ ʜ ɪ ʟ 𝼄 ɴ ɶ ʀ ʏ often mistaken by typing, uppercase alternatives to symbols shaped like small capitals
small capital q pharyngeal stop ʡ proposed for the pharyngeal stop of Formosan languages, ExtIPA for same purpose.
small capital q sokuon used by Japanologists.
Q capital Q used by Japanologists.
l l all coronal liquid consonants. broad transcription, mainly Koreanologists.
𝼆 𝼄 belted letters voiceless lateral fricatives (retroflex, palatal, velar, and alveolar) ɭ̊˔ ʎ̝̊ ʟ̝̊ now in the extIPA[6]
ʎ turned y alveolo-palatal lateral approximant [ʎ̟] or [l̠ʲ] broad transcription, mainly Koreanologists and Sinologists
ɲ n with left hook alveolo-palatal nasal [ɲ̟] or [n̠ʲ] broad transcription, mainly Koreanologists, Sinologists, and Japanologists
w with hook bilabial flap ⱱ̟
𝼈 turned r with long leg and retroflex hook retroflex lateral flap ɭ̆
ᶘ ᶚ esh or ezh with retroflex hook retroflex palato-alveolar fricatives ʃ͡ɻ ʒ͡ɻ may be impossible to pronounce[10]
ɏ barred y close central compressed vowel ÿ
ɏ small capital barred y near-close central compressed vowel ʏ̈
ұ barred straight y (Cyrillic straight u) near-close near-back unrounded vowel [ʊ̜] or [ɯ̽] used in Mande studies[11]
◌̣ underdot retroflex or r-colored vowels ɑ˞ etc.
k', t', etc. apostrophe no audible release , , etc. removed
k', t', etc. apostrophe palatalization , , etc. common in X-SAMPA
K T etc. uppercase letters (not small capitals) fortis , etc. used by some Koreanologists
ɔ̩ vowel with tilted line below lower-pitched rising / falling tone contour for languages that distinguish multiple rising or falling tones
turned comma above weak (sometimes normal) aspiration k t (sometimes ) First symbol may be left single quotation mark (U+2018) or modifier letter apostrophe (U+02BC); second symbol may be single high-reversed-9 quotation mark (U+201B) or modifier letter reversed comma (U+02BD)
ʦ ʣ ʧ ʤ ʨ ʥ ligatures affricates t͡s d͡z t͡ʃ d͡ʒ ʈ͡ʂ ɖ͡ʐ t͡ɕ d͡ʑ formerly acceptable variants[12]
𝼗 𝼒 ligatures with palatal hook palatalized affricates t͡ɕ d͡ʑ
𝼜 𝼙 ligatures with retroflex hook retroflex affricates ʈ͡ʂ ɖ͡ʐ John Laver used 𝼜 in Polish transcription[13]
p′ s′ t′ etc. prime palatalization etc. traditional Irish phonology transcription
etc. combining apostrophe palatalization etc. traditional Russian phonology transcription
* asterisk syntactic gemination (none) used in some Italian dictionaries
˹ open corner release/burst (none) IPA number 490
d d͡ɮ d͡z l ɫ ɬ ɮ ɺ n r ɹ ɾ s t t͡ɬ s z without diacritics dental consonants d̪͡ɮ̪ d̪͡z̪ ɫ̪ ɬ̪ ɮ̪ ɺ̪ ð̞ ɾ̪ t̪͡ɬ̪ t̪͡s̪ broad transcriptions; in some English dialects, /ð̞/ often described as ⟨ɹ̪⟩ for /rɹ/
β ð ʝ ɣ ʁ ʕ or e ø ɘ ɵ ɤ o without diacritics approximant consonants or mid vowels β̞ ð̞ j ɰ ʁ̞ ʕ̞ or ø̞ ə ɵ̞ ɤ̞ broad transcriptions; in Spanish, /j/ and /ɰ/ often described as ⟨ʝ̞⟩ and ⟨ɣ̞
ɛ œ ɜ ɞ ʌ ɔ without diacritics mid vowels ø̞ ə ɵ̞ ɤ̞ broad transcriptions; for example in some languages, // and // maybe described as ⟨ɛ̝⟩ and ⟨ɔ̝⟩, also /ə/ maybe described as ⟨ɘ̞⟩ or ⟨ɜ̝
ɪ ʊ a ɒ without diacritics central vowels ɪ̈ ʊ̈ ä ɒ̈ broad transcriptions; in some English dialects, /ä/ often described as ⟨ɑ̈⟩ in English for /ɑ/
c or ȼ c or stroked c voiceless alveolar affricate t͡s Americanist notation
ʒ ezh voiced alveolar affricate d͡z Americanist notation
y y voiced palatal approximant j Americanist notation
ä a with diaeresis near-open front unrounded vowel, open-mid front unrounded vowel or open front unrounded vowel æ, ɛ or a Uralicist notation
ö o with diaeresis close-mid front rounded vowel, open-mid front rounded vowel or mid front rounded vowel ø, œ or ø̞ Americanist and Uralicist notation
ü u with diaeresis close front rounded vowel or near-close near-front rounded vowel y or ʏ Americanist and Uralicist notation
k’ t’ etc. right single quotation mark Korean fortis etc. used by some Koreanists for fortis sounds; equivalent to ⟨k*⟩, etc. above.
◌⸋ box unreleased ◌̚ used where IPA ◌̚ would get confused with the corners used to indicate change of pitch in the Japanese pitch accent system
◌ʱ breathy/ voiced aspiration ◌̤
◌ˀ creaky voice/ glottalization ◌̰
◌̴ velarization ◌ˠ
ˉ◌, ˗◌, ˍ◌ high, mid and low-level tone or intonation removed
˭◌, ₌◌ extra-high and extra-low level tone or intonation removed
ˋ◌, ˴◌, ˎ◌ falling or high falling, mid falling and low-falling tone or intonation removed
ˊ◌, [NA], ˏ◌ (high) rising and low rising tone or intonation removed
ˇ◌, ˬ◌ (high) dipping and low dipping (falling-rising) tone or intonation removed
ˆ◌, ꞈ◌ peaking (rising-falling) tone or intonation removed
˜◌, ̰◌ "wavy" tone or intonation removed
˙◌, ·◌, .◌ atonic syllable with high, mid, and low pitch; respectively removed
◌́, ◌̂, ◌̀, ◌̆ Acute accent, circumflex, grave accent, breve stress symbols:

primary stress, weakened primary stress, secondary stress, and no stress; respectively

ˈˈ◌, ˈ◌, ˌ◌, ◌ some English phoneticians and phonologists use acute and grave accents as primary and secondary stress symbols. Some linguists[14] use the circumflex as weakened primary stress in compound words and the breve as no stress. these symbols are also written on the English spellings not just other IPA symbols.
◌̩, ◌̍ Vertical line below or above moraic used by Japanologists. In the standard IPA, these symbols represents syllabic sounds, but Japanologists use them for phonetic variants (except for nasal vowels) of the moraic N ([n̩, ɴ̩, ŋ̍ (or ŋ̩), ]).
◌̄, ◌́, ◌̌, ◌̀ Macron, acute accent, caron, grave accent Chinese tones ◌́, ◌̌, ◌̀, ◌̂ or similar, depending on dialect and analysis, or Chao tone letters used by Sinologists with the values the symbols have in Hanyu Pinyin. the standard IPA values of these diacritics are: mid, high, rising, and low tone.

See also

[edit]

Footnotes or references

[edit]
  1. ^ Ladefoged, Peter; Maddieson, Ian (1996). Sounds of the World's Languages. Oxford: Blackwell. pp. 313–314.
  2. ^ a b c d e f 1949 Principles of the IPA
  3. ^ a b c d e f g Henton, C. G. (1988). 5. Individual symbols and diacritics. Journal of the International Phonetic Association, 18(02), 85. doi:10.1017/s0025100300003686
  4. ^ 1912 Principles of the IPA
  5. ^ An impossible sound
  6. ^ a b "extIPA Symbols for Disordered Speech (Revised to 2015)" (PDF). Retrieved 15 February 2018.
  7. ^ a b Lee-Kim, Sang-Im (December 2014). "Revisiting Mandarin 'apical vowels': An articulatory and acoustic study". Journal of the International Phonetic Association. 44 (3): 261–282. doi:10.1017/S0025100314000267. S2CID 16432272.
  8. ^ Lee, Wai-Sum; Zee, Eric (June 2003). "Standard Chinese (Beijing)". Journal of the International Phonetic Association. 33 (1): 109–112. doi:10.1017/S0025100303001208.
  9. ^ Bailey, Charles-James N. (1976). "Some additions to the phonetic alphabet". Journal of the International Phonetic Association. 6 (1): 32–34. doi:10.1017/s002510030000147x. JSTOR 44525830.
  10. ^ Constable, Peter (2004). Revised Proposal to Encode Phonetic Symbols with Retroflex Hook in the UCS (PDF). p. 7.
  11. ^ Roberts, David; Boyd, Ginger; Merz, Johannes; Vydrin, Valentin (2020). "Quantifying written ambiguities in tone languages: A comparative study of Elip, Mbelime, and Eastern Dan". Language Documentation & Conservation. 14: 108–138. hdl:10125/24915.
  12. ^ Pullum, Geoffrey K.; William A. Ladusaw (1996). Phonetic Symbol Guide (2nd ed.). University of Chicago Press. p. 180. ISBN 0-226-68535-7.
  13. ^ Laver, John (1994). Principles of Phonetics. Cambridge University Press. p. 560.
  14. ^ Trager, George L., and Henry Lee Smith Jr. 1951. An Outline of English Structure. Studies in Linguistics: Occasional Papers 3. Norman, Okla.: Battenburg Press.