Zainab M. Musa and  Nordin M. A. Rahman and  Julaily A. Jusoh,  Validation of the Formal Model of Web Services Applications for Digital Reference Service of Library Information System.   journal   = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology.
    August 2015, vol. 104(8). 1952 - 1958
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