add link to count by distinct help article

README.md

@@ -268,7 +268,7 @@ This SDK automatically grabs useful data about the browser, including browser ty
 
 ### Setting Groups ###
 
-Amplitude supports assigning users to groups, and performing queries such as Count by Distinct on those groups. An example would be if you want to group your users based on what organization they are in by using an orgId. You can designate Joe to be in orgId 10, while Sue is in orgId 15. When performing an event segmentation query, you can then select Count by Distinct orgIds to query the number of different orgIds that have performed a specific event. As long as at least one member of that group has performed the specific event, that group will be included in the count. See our help article on [Count By Distinct]() for more information.
+Amplitude supports assigning users to groups, and performing queries such as Count by Distinct on those groups. An example would be if you want to group your users based on what organization they are in by using an orgId. You can designate Joe to be in orgId 10, while Sue is in orgId 15. When performing an event segmentation query, you can then select Count by Distinct orgIds to query the number of different orgIds that have performed a specific event. As long as at least one member of that group has performed the specific event, that group will be included in the count. See our help article on [Count By Distinct](https://amplitude.zendesk.com/hc/en-us/articles/218824237) for more information.
 
 When setting groups you need to define a `groupType` and `groupName`(s). In the above example, 'orgId' is a `groupType`, and the value 10 or 15 is the `groupName`. Another example of a `groupType` could be 'sport' with `groupNames` like 'tennis', 'baseball', etc.