diff --git a/Third-Party-Development-Details.md b/Third-Party-Development-Details.md
index d0c791d..de4b2c9 100644
--- a/Third-Party-Development-Details.md
+++ b/Third-Party-Development-Details.md
@@ -86,4 +86,10 @@ Hooks.once('init', () => {
         bpCost: 4
     };
 });
+```
+
+## Custom Attribution Sources
+If you want to add a new attribution source to the system you can register them with `CONFIG.DH.GENERAL.attributionSources` in the Foundry init hook.
+```js
+CONFIG.DH.GENERAL.attributionSources.forevermore = { label: "Forevermore", values: [{ label: "Campaign - Forevermore" }] }
 ```
\ No newline at end of file