> For the complete documentation index, see [llms.txt](https://docs.b2ihealthcare.com/snow-owl-authoring-platform/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.b2ihealthcare.com/snow-owl-authoring-platform/reference-sets/combining-reference-sets.md).

# Combining Reference Sets

Combining Reference Sets enables users to create a new Reference Set by merging two existing ones. Combining Reference Set option is available for Simple type Reference Sets.

The only supported referenced component type is SNOMED CT Concept.

Combining Reference Sets can be performed either by invoking the `Tools > Combine Reference Sets…`​ menu or by right-clicking on a Simple type Reference Set and selecting **Combine reference sets...***.*

<figure><img src="/files/4jMeSjDqE1SZygNWYvnA" alt=""><figcaption><p>Tools > Combine reference set</p></figcaption></figure>

<figure><img src="/files/tRIphL6TFCUSqVxS2Dzv" alt=""><figcaption><p>Reference Ste context menu</p></figcaption></figure>

The following methods are available to combine two Simple type Reference Sets named A and B:

| Method                                                            | Math Formula    | Description                                                          |
| ----------------------------------------------------------------- | --------------- | -------------------------------------------------------------------- |
| **Union**                                                         | `A U B`         | The resultant set contains all the elements in either A or B or both |
| **Intersection**                                                  | `A Ո B`         | The resultant set contains the elements present in both A and B      |
| **Complement**                                                    | `A-B - A\B`     | The resultant set contains everything in A but not present in B      |
| **Complement**                                                    | `B-A - B\A`     | The resultant set contains everything in B but not present in A      |
| <p><strong>Symmetric</strong><br><strong>difference</strong> </p> | `(A\B) U (B\A)` | The resultant set is the intersection subtracted from the union      |

![Combine Reference Sets](/files/-MHLDzQ6xeatqZMT9WVS)

After selecting one of them, click the **`Next`** button. To complete the operation, the Preferred Term for the new combined Reference Set needs to be set on the last wizard page.

![Combine Reference Sets – Properties](/files/-MHLF6gK54YL2CMkzWQd)

Hit the **`Finish`** button and the new Reference Set is created and its editor opens automatically.


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