WASET
    I. Sonia d’Apolito and  Bianca Sisinni and  Mirko Grimaldi and  Barbara Gili Fivela,  Perceptual and Ultrasound Articulatory Training Effects on English L2 Vowels Production by Italian Learners .   journal   = {International Journal of Cognitive and Language Sciences}, [online]. World Academy of Science, Engineering and Technology.
    July 2017, vol. 128(8). 2174 - 2181
    [viewed 26 April 2024]. Available from: https://publications.waset.org/pdf/10007865.