diff --git a/src/disease/query.py b/src/disease/query.py
index 0d72c3a..381b1e5 100644
--- a/src/disease/query.py
+++ b/src/disease/query.py
@@ -335,6 +335,9 @@ def _create_concept_mapping(
         ) -> ConceptMapping:
             """Create concept mapping for identifier
 
+            ``system`` will use OBO Foundry persistent URL (PURL), source homepage, or
+            namespace prefix, in that order of preference, if available.
+
             :param concept_id: Concept identifier represented as a curie
             :param relation: SKOS mapping relationship, default is relatedMatch
             :return: Concept mapping for identifier
diff --git a/src/disease/schemas.py b/src/disease/schemas.py
index d2dda2b..647dcf9 100644
--- a/src/disease/schemas.py
+++ b/src/disease/schemas.py
@@ -88,28 +88,28 @@ class NamespacePrefix(Enum):
     WIKIDATA = "wikidata"
 
 
-# Source to URI (from identifiers.org, if found)
+# Source to URI. Will use OBO Foundry persistent URL (PURL) or source homepage
 NAMESPACE_TO_SYSTEM_URI: dict[NamespacePrefix, str] = {
-    NamespacePrefix.NCIT: "https://www.ebi.ac.uk/ols4/ontologies/ncit/classes?short_form=NCIT_",
-    NamespacePrefix.MONDO: "https://monarchinitiative.org/MONDO:",
-    NamespacePrefix.DO: "https://www.ebi.ac.uk/ols4/ontologies/doid/terms?obo_id=DOID:",
-    NamespacePrefix.DOID: "https://www.ebi.ac.uk/ols4/ontologies/doid/terms?obo_id=DOID:",
-    NamespacePrefix.OMIM: "https://www.omim.org/entry/",
-    NamespacePrefix.ONCOTREE: "https://oncotree.mskcc.org/?version=oncotree_latest_stable&field=NAME&search=",
-    NamespacePrefix.EFO: "https://www.ebi.ac.uk/efo/EFO_",
-    NamespacePrefix.HP: "https://hpo.jax.org/app/browse/term/HP:",
-    NamespacePrefix.HPO: "https://hpo.jax.org/app/browse/term/HP:",
-    NamespacePrefix.KEGG: "https://www.kegg.jp/entry/",
-    NamespacePrefix.MEDDRA: "https://purl.bioontology.org/ontology/MEDDRA/",
+    NamespacePrefix.NCIT: "http://purl.obolibrary.org/obo/ncit.owl",
+    NamespacePrefix.MONDO: "http://purl.obolibrary.org/obo/mondo.owl",
+    NamespacePrefix.DO: "http://purl.obolibrary.org/obo/doid.owl",
+    NamespacePrefix.DOID: "http://purl.obolibrary.org/obo/doid.owl",
+    NamespacePrefix.OMIM: "https://www.omim.org",
+    NamespacePrefix.ONCOTREE: "https://oncotree.mskcc.org",
+    NamespacePrefix.EFO: "https://www.ebi.ac.uk/efo",
+    NamespacePrefix.HP: "http://purl.obolibrary.org/obo/hp.owl",
+    NamespacePrefix.HPO: "http://purl.obolibrary.org/obo/hp.owl",
+    NamespacePrefix.KEGG: "https://www.genome.jp/kegg/disease/",
+    NamespacePrefix.MEDDRA: "https://www.meddra.org/",
     NamespacePrefix.MEDGEN: "https://www.ncbi.nlm.nih.gov/medgen/",
     NamespacePrefix.MESH: "https://id.nlm.nih.gov/mesh/",
-    NamespacePrefix.MP: "https://www.ebi.ac.uk/ols4/ontologies/mp/terms?obo_id=MP:",
-    NamespacePrefix.OBI: "https://purl.obolibrary.org/obo/",
-    NamespacePrefix.ORPHANET: "https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=",
-    NamespacePrefix.PATO: "https://www.ebi.ac.uk/ols4/ontologies/pato/terms?obo_id=PATO:",
-    NamespacePrefix.UMLS: "https://linkedlifedata.com/resource/umls/id/",
-    NamespacePrefix.WIKIPEDIA: "https://en.wikipedia.org/wiki/",
-    NamespacePrefix.WIKIDATA: "https://www.wikidata.org/entity/",
+    NamespacePrefix.MP: "http://purl.obolibrary.org/obo/mp.owl",
+    NamespacePrefix.OBI: "http://purl.obolibrary.org/obo/obi.owl",
+    NamespacePrefix.ORPHANET: "https://www.orpha.net",
+    NamespacePrefix.PATO: "http://purl.obolibrary.org/obo/pato.owl",
+    NamespacePrefix.UMLS: "https://www.nlm.nih.gov/research/umls/index.html",
+    NamespacePrefix.WIKIPEDIA: "https://en.wikipedia.org",
+    NamespacePrefix.WIKIDATA: "https://www.wikidata.org",
 }
 
 # URI to source
@@ -318,21 +318,21 @@ class NormalizationService(BaseModel):
                         {
                             "coding": {
                                 "code": "0004355",
-                                "system": "https://monarchinitiative.org/MONDO:",
+                                "system": "http://purl.obolibrary.org/obo/mondo.owl",
                             },
                             "relation": "relatedMatch",
                         },
                         {
                             "coding": {
                                 "code": "7757",
-                                "system": "https://www.ebi.ac.uk/ols4/ontologies/doid/terms?obo_id=DOID:",
+                                "system": "http://purl.obolibrary.org/obo/doid.owl",
                             },
                             "relation": "relatedMatch",
                         },
                         {
                             "coding": {
                                 "code": "C1332977",
-                                "system": "https://linkedlifedata.com/resource/umls/id/",
+                                "system": "https://www.nlm.nih.gov/research/umls/index.html",
                             },
                             "relation": "relatedMatch",
                         },
diff --git a/tests/data/do/do_20240731.owl b/tests/data/do/do_20240731.owl
index b8cc5f8..b926993 100644
--- a/tests/data/do/do_20240731.owl
+++ b/tests/data/do/do_20240731.owl
@@ -801,7 +801,7 @@
         <owl:annotatedSource rdf:resource="http://purl.obolibrary.org/obo/DOID_0080601"/>
         <owl:annotatedProperty rdf:resource="http://purl.obolibrary.org/obo/IAO_0000115"/>
         <owl:annotatedTarget xml:lang="en">A benign neoplasm that derives_from germ cells.</owl:annotatedTarget>
-        <oboInOwl:hasDbXref>url:https://en.wikipedia.org/wiki/Germ_cell_tumor</oboInOwl:hasDbXref>
+        <oboInOwl:hasDbXref>url:https://en.wikipedia.orgGerm_cell_tumor</oboInOwl:hasDbXref>
     </owl:Axiom>
 
 
diff --git a/tests/data/mondo/mondo_20241203.obo b/tests/data/mondo/mondo_20241203.obo
index e354b7f..70a997c 100644
--- a/tests/data/mondo/mondo_20241203.obo
+++ b/tests/data/mondo/mondo_20241203.obo
@@ -76,7 +76,7 @@ property_value: terms:source http://purl.obolibrary.org/obo/ncbitaxon.owl
 property_value: terms:source http://purl.obolibrary.org/obo/ncit.owl
 property_value: terms:source http://purl.obolibrary.org/obo/uberon.owl
 property_value: terms:source http://www.orpha.net/ontology/orphanet.owl
-property_value: terms:source https://id.nlm.nih.gov/mesh/
+property_value: terms:source https://identifiers.org/mesh:
 property_value: terms:source https://rarediseases.info.nih.gov/
 
 [Term]
diff --git a/tests/unit/test_query.py b/tests/unit/test_query.py
index 10f5614..da6eaaf 100644
--- a/tests/unit/test_query.py
+++ b/tests/unit/test_query.py
@@ -26,28 +26,28 @@ def neuroblastoma():
             {
                 "coding": {
                     "code": "0005072",
-                    "system": "https://monarchinitiative.org/MONDO:",
+                    "system": "http://purl.obolibrary.org/obo/mondo.owl",
                 },
                 "relation": "relatedMatch",
             },
             {
                 "coding": {
                     "code": "NBL",
-                    "system": "https://oncotree.mskcc.org/?version=oncotree_latest_stable&field=NAME&search=",
+                    "system": "https://oncotree.mskcc.org",
                 },
                 "relation": "relatedMatch",
             },
             {
                 "coding": {
                     "code": "769",
-                    "system": "https://www.ebi.ac.uk/ols4/ontologies/doid/terms?obo_id=DOID:",
+                    "system": "http://purl.obolibrary.org/obo/doid.owl",
                 },
                 "relation": "relatedMatch",
             },
             {
                 "coding": {
                     "code": "C0027819",
-                    "system": "https://linkedlifedata.com/resource/umls/id/",
+                    "system": "https://www.nlm.nih.gov/research/umls/index.html",
                 },
                 "relation": "relatedMatch",
             },
@@ -58,7 +58,7 @@ def neuroblastoma():
             {
                 "coding": {
                     "code": "0000621",
-                    "system": "https://www.ebi.ac.uk/efo/EFO_",
+                    "system": "https://www.ebi.ac.uk/efo",
                 },
                 "relation": "relatedMatch",
             },
@@ -73,14 +73,14 @@ def neuroblastoma():
             {
                 "coding": {
                     "code": "635",
-                    "system": "https://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=",
+                    "system": "https://www.orpha.net",
                 },
                 "relation": "relatedMatch",
             },
             {
                 "coding": {
                     "code": "C2751421",
-                    "system": "https://linkedlifedata.com/resource/umls/id/",
+                    "system": "https://www.nlm.nih.gov/research/umls/index.html",
                 },
                 "relation": "relatedMatch",
             },
@@ -136,7 +136,7 @@ def mafd2():
         label="major affective disorder 2",
         mappings=[
             {
-                "coding": {"code": "309200", "system": "https://www.omim.org/entry/"},
+                "coding": {"code": "309200", "system": "https://www.omim.org"},
                 "relation": "relatedMatch",
             },
             {
@@ -153,7 +153,7 @@ def mafd2():
             {
                 "coding": {
                     "code": "C1839839",
-                    "system": "https://linkedlifedata.com/resource/umls/id/",
+                    "system": "https://www.nlm.nih.gov/research/umls/index.html",
                 },
                 "relation": "relatedMatch",
             },