Identifying the source of Budgeted and Actual Non-Labor Units that do not have Resources assigned to them

Hello,

I am taking over maintaining a schedule and do not know how to find the source of some Nonlabor Units that are being expended.

There are budgeted and actualized non-labor units for activities such as "Execute Contract" and "Prefab Meeting", but I don't see anything under Resources, Resource IDs, Cost Accounts, or Cost Account IDs.

These activities do not seem like they require any labor or non-labor resources.  I am concerned that this is going to come up as a question during the schedule update review.  Where can I find out what the units represent?  How can I remove them, or do I need to?

Thanks for your help.

Greg