1. Study on Architecture Enhancements to Support Group Communication System Enablers for LTE (GCSE_LTE)
https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=873
2. Service Aspects and Requirements for Network Sharing
https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=705
3. Mission Critical Push To Talk (MCPTT) over LTE.; Stage 1
https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=623
4. Feasibility Study for Proximity Services (ProSe) (Release 12)
https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=653
5. Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall Descriptions; Stage 2
https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=2430