Different standards of ELF (SysV vs TIS) and Linux?

There are at least two standards of [Executable and Linkable Format (ELF)](https://en.wikipedia.org/wiki/Executable_and_Linkable_Format) , one of them * [System V Application Binary Interface AMD64 Architecture Processor Supplement (With LP64 and ILP32 Programming Models) Version 1.0](https://raw.githubusercontent.com/wiki/hjl-tools/x86-psABI/x86-64-psABI-1.0.pdf) * [Tool Interface Standard (TIS) Executable and Linking Format (ELF) Specification Version 1.2](http://refspecs.linuxbase.org/elf/elf.pdf) The older one, the TIS ELF Standard 1.2 is 106 pages while the SysV ABI is 157 pages but covers ELF only on pages 63-86 (23 pages). How do these two standards relate to each other? And which one does Linux and GNU Linker use? What is the Tool Interface Standard?