outlink also for DOI

ippisite/ippidb/models.py

@@ -102,11 +102,13 @@ class Bibliography(AutoFillableModel):
         Bibliography.validate_source_id(self.id_source, self.source)
 
     def has_external_url(self):
-        return self.source == 'PM'
+        return self.source == 'PM' or self.source == 'DO'
 
     def get_external_url(self):
         if self.source == 'PM':
             return "https://www.ncbi.nlm.nih.gov/pubmed/" + str(self.id_source)
+        if self.source == 'DO':
+            return "https://doi.org/" + str(self.id_source)
 
     @staticmethod
     def validate_source_id(id_source, source):