CHEMISTRY COMMUNITY

In 9C.3, one of the compounds is sodium bisoxalato(diaqua)ferrate(III). Why is diaqua in parentheses?
In 9C.4, there's another compound called barium tris(oxalato)ferrate(III). Why is oxalato in parentheses here but not in the other one?
Are there other times when you use parentheses in naming?

I thought that polydentate ligands were put in parentheses when there is multiple of them and that explains 9C.4 but not 9C.3 so i'm confused too