Jonathan D. Rosenberg. The Session Initiation Protocol (SIP) UPDATE Method. RFC, 3311:1-13, October 2002. [doi]
@article{rfc3311, title = {The Session Initiation Protocol (SIP) UPDATE Method}, author = {Jonathan D. Rosenberg}, year = {2002}, month = {October}, doi = {10.17487/RFC3311}, url = {https://doi.org/10.17487/RFC3311}, researchr = {https://researchr.org/publication/rfc3311}, cites = {0}, citedby = {0}, journal = {RFC}, volume = {3311}, pages = {1-13}, }