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# add(_:position:)

Adds an existing reference arc to the prim.

```
func add(_ reference: USDPrim.Reference, position: USDPrim.ListPosition = .backOfPrependList) throws
```

## Parameters

`reference`

The reference to add.

`position`

Where to insert the reference in the prim’s reference list.

## Discussion> Throws: An error if the reference cannot be added.

---

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