Yong Zhang and  Ruimin Hu,  A High Quality Speech Coder at 600 bps.   journal   = {International Journal of Electronics and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    November 2009, vol. 35(11). 2044 - 2049
    [viewed 23 October 2019]. Available from: https://publications.waset.org/pdf/5166.