-- a weird and unintended consequence of using
--   Ring ** Ring := Ring => tensor
-- is that the documentation maker uses the "options" function on the key (symbol **,Ring,Ring),
-- finds the function "tensor" with "lookup", and gets its options, which is not right!
-- This will require some thinking to prevent in the future.
Ring ** Ring := Ring => (R,S) -> tensor(R,S)
