diff --git a/Contributing.md b/Contributing.md
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--- a/Contributing.md
+++ b/Contributing.md
@@ -1,6 +1,6 @@
 # Coding Conventions
 
-HAPI FHIR uses the `java.annotation.Nullable` and `javax.annotation.Nonnull` annotations (where relevant and useful), as opposed to the equivalent `org.jetbrains` annotations. See [this StackOverflow] for a description on how to set this in IntelliJ.
+HAPI FHIR uses the `java.annotation.Nullable` and `javax.annotation.Nonnull` annotations (where relevant and useful), as opposed to the equivalent `org.jetbrains` annotations. See [this StackOverflow](https://stackoverflow.com/questions/43372109/notnull-nonnull-etc-all-dont-work-in-intellij-idea?rq=1) for a description on how to set this in IntelliJ.
 
 # Code Style