diff --git a/sourcing/model.py b/sourcing/model.py
index 6ccf03f..71f5e72 100644
--- a/sourcing/model.py
+++ b/sourcing/model.py
@@ -122,6 +122,14 @@ class User(TimeStampedModel, UserMixin):
             raise LoginError('incorrect password')
         return user
 
+class Reference(Base):
+    __tablename__ = 'reference'
+    subject_id = Column(Integer, ForeignKey('item.id'), primary_key=True)
+    object_id = Column(Integer, ForeignKey('item.id'), primary_key=True)
+
+    subject_item = relationship('User', backref='objects')
+    object_item = relationship('User', backref='subjects')
+
 class Item(TimeStampedModel):
     __tablename__ = 'item'
     __versioned__ = {'base_classes': (TimeStampedModel,)}
@@ -134,6 +142,15 @@ class Item(TimeStampedModel):
     filename = Column(Unicode)
     text = Column(UnicodeText)
 
+    subjects = relationship('item',
+                            secondary='reference',
+                            # backref='object_item',
+                            primaryjoin=id == Reference.object_id)
+    objects = relationship('item',
+                           secondary='reference',
+                           # backref='subjects_item',
+                           primaryjoin=id == Reference.subject_id)
+
     user = relationship('User', backref='items')
 
     __mapper_args__ = {