Hi,
it's been quite a while since I applied for registration. There were no "validation of work history" templates around, as I have seen in the current application package.
So, cannot say how you best refer to the references. Mine were part of my "numbered" system.
BUT: If you leave them unopened, you cannot refer to them - as you don't know what they say. So, why don't you just use them as what they are = validation of employment record.
And as evidence use additional stuff like performance appraisals, feedback on IST sessions that you have given, rotational objectives sign off, ?on-call competencies, training records, peer reviews etc..

? Does this help?
Cheers,
Fyzzio