Some of the comments refer to the paper at http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2018/p136..., which was the original submitted URL.
Response to “Fibers under the magnifying glass”: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p086...
Response to response to "Fibers under the magnifying glass": http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p152...
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p086....
And Response to response to "Fibers under the magnifying glass", at
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p152...
Gor so far seems to be ahead as stackless coroutines are part of the standard.