Sa’ed Abed and Mohammad H. Al Shayeji and Ovais Ahmed and Sahel Alouneh, Formal Specification and Description Language and Message Sequence Chart to Model and Validate Session Initiation Protocol Services. journal = {International Journal of Computer and Information Engineering}, [online]. World Academy of Science, Engineering and Technology. February 2016, vol. 111(3). 534 - 542 [viewed 25 April 2024]. Available from: https://publications.waset.org/pdf/10004038.