Added helpful comment

import/marc.properties

@@ -17,6 +17,7 @@ allfields = custom, getAllSearchableFieldsAsSet(100, 900)
 language = 008[35-37]:041a:041d:041h:041j, language_map.properties
 format = custom, getFormat, format_map.properties
 
+# see $VUFIND_HOME/config/vufind/author-classification.ini for relator definitions
 author                = custom, getAuthorsFilteredByRelator(100abcd:700abcd,100,firstAuthorRoles)
 author_variant        = custom, getAuthorInitialsFilteredByRelator(100a:700a,100,firstAuthorRoles)
 author_fuller         = custom, getAuthorsFilteredByRelator(100q:700q,100,firstAuthorRoles)