WASET
    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
    [viewed 29 March 2024]. Available from: https://publications.waset.org/pdf/10002386.