diff --git a/wmdr/unit/h.ttl b/wmdr/unit/h.ttl
index 01c6dde4..5a6c80c9 100644
--- a/wmdr/unit/h.ttl
+++ b/wmdr/unit/h.ttl
@@ -2,7 +2,7 @@
 @prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix dct: <http://purl.org/dc/terms/> . 
 
-<h> a skos:Concept ;
-	rdfs:label "hour" ;
-	skos:notation "h" ;
-	dct:description "Unit of time, accepted for use with SI: 1 h = 3600 s"@en	.
+<H> a skos:Concept ;
+	rdfs:label "henry" ;
+	skos:notation "H" ;
+	dct:description "SI derived unit of electrical inductance; SI base unit equivalent: kg.m2.s-2.A-2"@en	.
diff --git a/wmdr/unit/s.m-1.ttl b/wmdr/unit/s.m-1.ttl
index fca26169..a2b1360a 100644
--- a/wmdr/unit/s.m-1.ttl
+++ b/wmdr/unit/s.m-1.ttl
@@ -2,7 +2,7 @@
 @prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix dct: <http://purl.org/dc/terms/> . 
 
-<s.m-1> a skos:Concept ;
-	rdfs:label "second per metre" ;
-	skos:notation "s.m-1" ;
-	dct:description "SI derived unit of quantity with dimension of T.L-1"@en	.
+<S.m-1> a skos:Concept ;
+	rdfs:label "siemens per metre" ;
+	skos:notation "S.m-1" ;
+	dct:description "SI derived unit of spatial gradient of electric conductance"@en	.
diff --git a/wmdr/unit/s.ttl b/wmdr/unit/s.ttl
index ad9ed9f1..bf58bd83 100644
--- a/wmdr/unit/s.ttl
+++ b/wmdr/unit/s.ttl
@@ -2,7 +2,7 @@
 @prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix dct: <http://purl.org/dc/terms/> . 
 
-<s> a skos:Concept ;
-	rdfs:label "second" ;
-	skos:notation "s" ;
-	dct:description "SI base unit of time"@en	.
+<S> a skos:Concept ;
+	rdfs:label "siemens" ;
+	skos:notation "S" ;
+	dct:description "SI derived unit of electrical conductance; SI base unit equivalent: kg-1.m-2.s3.A2"@en	.
diff --git a/wmdr/unit/t.ttl b/wmdr/unit/t.ttl
index 083f7235..c45324b3 100644
--- a/wmdr/unit/t.ttl
+++ b/wmdr/unit/t.ttl
@@ -2,7 +2,7 @@
 @prefix rdfs:  <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix dct: <http://purl.org/dc/terms/> . 
 
-<t> a skos:Concept ;
-	rdfs:label "tonne" ;
-	skos:notation "t" ;
-	dct:description "Unit of mass, accepted for use with SI; SI base unit equivalent: 1000 kg"@en	.
+<T> a skos:Concept ;
+	rdfs:label "tesla" ;
+	skos:notation "T" ;
+	dct:description "SI derived unit of magnetic induction, magnetic flux density; SI base unit equivalent: kg.s-2.A-1"@en	.