Hi. SQL plus is telling me "ORA-00936: missing expression" when I execute:
update KingsDepartments
set Professors = Professors_T(
(select Ref(O) from KingsCS O where O.Name = 'Professor Adam'), (select Ref(O2) from KingsCS O2 where O2.Name = 'Professor Alan'))
where Name = 'Computer Science';

And an asterix is placed under the first select. KingsDepartments is a table of Department_T objects, which contain a field Professors_T. Professors_T is a table of oids of objects of the same type as KingsCS contains.
Any idea why I'm getting this error?

Thanks in advance.