51. The expert from SAE International presented GRVA-13-28/Rev.1, introducing GRVA-13-26 and GRVA-13-29, proposing updates to references to ISO/SAE 21343 in the interpretation document for UN Regulation No. 155 and proposing clarifications in UN Regulation No. 155 regarding the authentication of Global Navigation Satellite System (GNSS) messages. GRVA requested the secretariat to distribute GRVA-13-26 and GRVA-13-29 with official symbols at the next session with the necessary changes to produce: (i) an amendment proposal to UN Regulation No. 155 and (ii) an amendment proposal to the interpretation document.