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Here's the listing I've been working with: https://yaledevelopmentyale.service-now.com/sys_user_has_role_list.do
I've been working with Alan at Fruition to build up a list of Financial Approver group members who are not also members of any other assignment group. He came up with:
https://yaledevelopmentyale.service-now.com/financial_approvers_singleton_members.do
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The method to get the real answer people wanted from me is:
https://yaledevelopmentyale.service-now.com/itil_without_finance_approver_singletons.do