Generally the nucleic acid and the proteins of a virus self-assemble together, so both are crucial for the stability of the virion. I hope this can help you.

Try this review, looks quite interesting.

Assembly, stability and dynamics of virus capsids.

Mateu MG

Arch Biochem Biophys. 2013 Mar;531(1-2):65-79. doi: 10.1016/j.abb.2012.10.015. Epub 2012 Nov 8.

Capsid and nucleic acids are in the inner core that normally do not have any so called matrix. Some membrance-bound of virions may have matrix outside of capsid. Influenza virus is a good example.

Hi Paolo, would you have the pdf of your reference? Thanks in advance.