Cheng-Suan Lee and  Khong Neng Choong and  So Gean Koh and  Chee Onn Chow and  Mazlan Abbas,  Performance Study on Audio Codec and Session Transfer of Open Source VoIP applications.   journal   = {International Journal of Information and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    December 2009, vol. 36(12). 2281 - 2287
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