diff --git a/src/caoscrawler/sync_graph.py b/src/caoscrawler/sync_graph.py
index d317b0c89a9d8a73dfe78d75aaeab0b4b3b2f511..7589b556c3c70cf4124aec79cb41db3212a9c364 100644
--- a/src/caoscrawler/sync_graph.py
+++ b/src/caoscrawler/sync_graph.py
@@ -158,12 +158,12 @@ class SyncGraph():
 
         # initialize reference mappings (see _create_reference_mapping)
         (
-            self.forward_references,
-            self.backward_references,
-            self.forward_references_id_props,
-            self.backward_references_id_props,
-            self.forward_references_backref,
-            self.backward_references_backref,
+            self.forward_references,  # full set of reference properties of the entity
+            self.backward_references,  # full set of reference properties (of other entities) that reference the entity
+            self.forward_references_id_props,  # subset of the reference properties that are part of identifiables
+            self.backward_references_id_props,  # subset of the backward references that are part of identifiables
+            self.forward_references_backref,  # subset of the reference properties that are part of identifiables as "referenced_by" properties
+            self.backward_references_backref,  # same for backward references
         ) = self._create_reference_mapping(self.nodes)
 
         # remove entities with path or ID from unchecked list
@@ -247,6 +247,8 @@ class SyncGraph():
         """
         If a record for which it could not yet be verified whether it exists in LA or not is part
         of the identifying properties, this returns True, otherwise False
+
+        Last review by Alexander Schlemmer on 2024-05-27.
         """
 
         return any([id(ent) not in self._missing and id(ent) not in self._existing