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Wikström (2013:45), "It seems to be the case that younger RP or near-RP speakers typically use a closer quality, possibly approaching Cardinal 6 considering that the quality appears to be roughly intermediate between that used by older speakers for the LOT vowel and that used for the THOUGHT vowel, while older speakers use a more open quality, between Cardinal Vowels 13 and 6." Wikström, Jussi (2013), "An acoustic study of the RP English LOT and THOUGHT vowels", Journal of the International Phonetic Association, 43 (1): 37–47, doi:10.1017/S0025100312000345, S2CID146863401
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Peters (2006:118–119) Peters, Jörg (2006), "The dialect of Hasselt", Journal of the International Phonetic Association, 36 (1): 117–124, doi:10.1017/S0025100306002428
Wikström (2013:45), "It seems to be the case that younger RP or near-RP speakers typically use a closer quality, possibly approaching Cardinal 6 considering that the quality appears to be roughly intermediate between that used by older speakers for the LOT vowel and that used for the THOUGHT vowel, while older speakers use a more open quality, between Cardinal Vowels 13 and 6." Wikström, Jussi (2013), "An acoustic study of the RP English LOT and THOUGHT vowels", Journal of the International Phonetic Association, 43 (1): 37–47, doi:10.1017/S0025100312000345, S2CID146863401
