Closes #1470

CppCoreGuidelines.md

@@ -19045,6 +19045,10 @@ Avoid clients of a header having to manage that header's dependencies.
 
 Failing to follow this results in difficult to diagnose errors for clients of a header.
 
+##### Note
+
+A header should include all its dependencies. Be careful about using relative paths because C++ implementations diverge on their meaning.
+
 ##### Enforcement
 
 A test should verify that the header file itself compiles or that a cpp file which only includes the header file compiles.