purevowel,purecolor

【预订】pure vowel sounds and tone production 9781161569322
【预订】pure vowel sounds and tone production 9781169196704
ppt vowelspurevowels单元音diphthongs双元音 purevowels front
ppt vowelspurevowels单元音diphthongs双元音 purevowels front
english vowels & vowel classification the english pure vowels