Unambigous restraints with specific atoms

What is the CNS format for writing unambigous restraints with specific atoms instead of just the entire residues. For example I want to set the upper distance limit for the alpha carbon of residue 229 to 4Å. How would I do that?

Described in our original Nature Protocol 2010 paper.

One example here:

assign (resid 10 and name CA and segid A) (resid 20 and name CA and segid B) 4.0 4.0 0.0

And also described for example in the following online tutorial: