diff --git a/src/caoscrawler/sync_graph.py b/src/caoscrawler/sync_graph.py
index 71b1f7eb8b654245a3794395ebfbf69a67270deb..72bd3bd23c05aa41d707a6f3b62020ee5dc5f29a 100644
--- a/src/caoscrawler/sync_graph.py
+++ b/src/caoscrawler/sync_graph.py
@@ -158,12 +158,14 @@ class SyncGraph():
 
         # initialize reference mappings (see _create_reference_mapping)
         (
-            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.forward_references,  # id(node) -> full set of nodes referenced by the given node
+            self.backward_references,  # id(node) -> full set of nodes referencing the given node
+            # as above, subset where the reference properties are part of identifiables
+            self.forward_references_id_props,
+            self.backward_references_id_props,
+            # as above, subset where references are part of identifiables due to "referenced_by"
+            self.forward_references_backref,
+            self.backward_references_backref,
         ) = self._create_reference_mapping(self.nodes)
 
         # remove entities with path or ID from unchecked list