Non-locality of the C- and D-theories
  Apparent similarities between non-local theories of gravity and the so-called
C-theories are pointed out. It is shown that some simple C-theories can be
mapped exactly into a previously considered type of ghost-free nonlocal
gravity. This may introduce a useful tool to tackle some infinite-order
derivative theories and raises the possibility of describing renormalisable
gravity in a new context of D-theories.
