How can I get the user that approve a promotion request using alias attributes?

I'm trying to use alias attribute to dsiplat some informations from a promotion request as attributes on a document.

I got to display the promotion request number and the promotion date using alias attributes, but I also need to display the user that aproves this promotion request.

For date and number promotion request, I use the following mapping:

roleBObject@wt.maturity.PromotionTarget~roleAObject^wt.maturity.PromotionNotice~promotionDate

roleBObject@wt.maturity.PromotionTarget~roleAObject^wt.maturity.PromotionNotice~number

But for approver, I use the following mapping but no value is displayed:

roleBObject@wt.maturity.PromotionTarget~roleAObject^wt.maturity.PromotionNotice~roleBObject^wt.workflow.engine.WfVotingEventAudit~workCompletedBy

If anyone could provide some support, I would appreciate it.

Wesley