In anonymous credentials schemes, it is possible to anonymously prove knowledge of a signature. Proposals for anonymous credentials with attributes also include a method for proving statements about the signed attributes in zero-knowledge, i.e. proving to a third party verifier that the signed values are the opening of a commitment. For example if I have a credential which is a signature on my current income, it is valuable to be able to prove to a third party that a committed value opens to the same income, without disclosing my actual income.
Reading the Pointcheval-Sanders proposal for anonymous credentials, I cannot find any description for how to prove relations of the signed attributes to a commitment. Is there any publication describing such a procedure?