diff --git a/sok/models.py b/sok/models.py
index 4e83a51..3f6b7e6 100644
--- a/sok/models.py
+++ b/sok/models.py
@@ -103,6 +103,24 @@ class Publication(models.Model):
 	def relevant_referenced_by(self) -> QuerySet:
 		return self.referenced_by.filter(exclusion_criteria__isnull=True)
 
+	def stage_added(self) -> int:
+		if not self.is_relevant:
+			return 10000
+
+		if self.sources.exists():
+			return 0
+
+		if self.referenced_by.filter(exclusion_criteria__isnull=True, sources__isnull=False) or  self.references.filter(exclusion_criteria__isnull=True, sources__isnull=False):
+			return 1
+
+		if ref_by := self.referenced_by.filter(exclusion_criteria__isnull=True):
+			stages = set([ref.stage_added() for ref in ref_by])
+			return 1 + sorted(stages)[0]
+
+		if refs := self.references.filter(exclusion_criteria__isnull=True):
+			stages = set([ref.stage_added() for ref in refs])
+			return 1 + sorted(stages)[0]
+
 	@property
 	def stage(self) -> Optional[str]:
 		if not self.is_relevant:
@@ -113,24 +131,27 @@ class Publication(models.Model):
 			return 'primary'
 
 		# Referenced by primary (backward snowballing)
-		# TODO make transitive
+		# DONE make transitive
 		if self.referenced_by.filter(exclusion_criteria__isnull=True, sources__isnull=False):
 			return 'secondary'
 
 		# References a primary (forward snowballing)
-		# TODO make transitive
 		if self.references.filter(exclusion_criteria__isnull=True, sources__isnull=False):
 			return 'tertiary'
 
-		if ref_by := self.referenced_by.filter(exclusion_criteria__isnull=True):
-			stages = set([ref.stage for ref in ref_by])
-			if 'secondary' in stages: return 'sec-secondary'
-			elif 'tertiary' in stages: return 'sec-tertiary'
+		# prefer secondary over tertiary regardless of stage for now
+		exclude = False
+		if self.referenced_by.filter(exclusion_criteria__isnull=True):
+			stage = self.stage_added()
+			if stage > 10000: exclude = True
+			else: return str(stage) + '-secondary'
 
-		if refs := self.references.filter(exclusion_criteria__isnull=True):
-			stages = set([ref.stage for ref in ref_by])
-			if 'secondary' in stages: return 'tert-secondary'
-			elif 'tertiary' in stages: return 'tert-tertiary'
+		if self.references.filter(exclusion_criteria__isnull=True):
+			stage = self.stage_added()
+			if stage > 10000: return 'excluded-by-ref'
+			else: return str(stage) + '-tertiary'
+
+		if exclude: return 'excluded-by-ref'
 
 		return None