[NTG-context] m-bib and \onlinecite

Hello, what is the recommended way to get the following: as is written in Ref.~4. Using Ref.~\cite[four] gives "Ref. [4]" with the superfluous brackets. (\cite[ref] should remain unmodified, ie with brackets, as this is mostly used in texts [1-5,7].) APS' revtex offers \onlinecite (Ref.~\onlinecite{four}) to obtain the reference number without the brackets. Tobias