Can I used to different output style in one library?

Hi,

I am writing a paper and using Harvard style for reference; however, I need to cite some government document so can I set Harvard press-politic style for a specific reference?

For example: I want to cite Green Paper (1977) but with the Harvard style it becomes Paper, G. (1977)

Please help me with some tricks to solve this problem.

Thank you,

ellie

Thank you

ellie