1. 3GPP 2016a 3gpp TS 23.281, functional architecture and information flows to support mission critical video (MCVideo); stage 2 https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=3087
2. 3GPP 2016b 3gpp TS 23.282, functional architecture and information flows to support mission critical data (MCData); stage 2 https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=3088
3. 3GPP 2016c 3gpp TS 23.303 v12.2.0, proximity-based services (ProSe); stage 2 (release 12) https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=840
4. 3GPP 2016d 3gpp TS 23.379, functional architecture and information flows to support mission critical push to talk (MCPTT); stage 2 https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=3089
5. 3GPP TR 36.843, Study on LTE device to device proximity services; Radio aspects , v12.0.1 2014