It took me a minute with a few googles, but the TS in this case means "Technical Specification", which helped out a ton with searching.

Unfortunately, I'm still not 100% this is what they're referring to, but I think this is it.

https://isocpp.org/files/papers/n3996.pdf

EDIT: Here it is :D

https://www.meetingcpp.com/blog/items/reflections-on-the-ref...

It's a proposal for inclusion into the C++ standard.