Attempt to clarify environment marker evaluation

source/specifications/core-metadata.rst

@@ -574,7 +574,7 @@ The format of a requirement string contains from one to four parts:
 * An environment marker after a semicolon. This means that the
   requirement is only needed in the specified conditions.
 
-See :pep:`508` for full details of the allowed format.
+See :ref:`dependency-specifiers` for full details of the allowed format.
 
 The project names should correspond to names as found
 on the `Python Package Index`_.

source/specifications/dependency-groups.rst

@@ -209,8 +209,8 @@ The output is therefore valid ``requirements.txt`` data.
         realized_group = []
         for item in raw_group:
             if isinstance(item, str):
-                # packaging.requirements.Requirement parsing ensures that this is a valid
-                # PEP 508 Dependency Specifier
+                # packaging.requirements.Requirement parsing ensures that this
+                # is a valid dependency specifier
                 # raises InvalidRequirement on failure
                 Requirement(item)
                 realized_group.append(item)