diff --git a/src/MDConcLengths.php b/src/MDConcLengths.php
index 4066c8f..9254337 100644
--- a/src/MDConcLengths.php
+++ b/src/MDConcLengths.php
@@ -92,6 +92,7 @@ final class MDConcLengths implements MDImporterConcordanceListInterface {
             "5cm",
             "Zentimeter",
             "см",
+            "",
             "ca" => MDLengthUnit::cm,
 
             "Meter",
diff --git a/src/MDConcMeasurementTypes.php b/src/MDConcMeasurementTypes.php
index 1fa00a8..ecd806c 100644
--- a/src/MDConcMeasurementTypes.php
+++ b/src/MDConcMeasurementTypes.php
@@ -152,6 +152,11 @@ final class MDConcMeasurementTypes implements MDImporterConcordanceListInterface
             "Auflagekarton Standardformat",
             "Suffix",
             "HxBxT",
+            "CC",
+            "Eisen",
+            "mm",
+            "Größe",
+            "CdV",
             "Stichhöhe (Höhe x Breite)" => false,
 
             "Höhe",
diff --git a/src/MDConcSourceTypes.php b/src/MDConcSourceTypes.php
index 2b20ba2..b5465d2 100644
--- a/src/MDConcSourceTypes.php
+++ b/src/MDConcSourceTypes.php
@@ -17,6 +17,7 @@ final class MDConcSourceTypes implements MDImporterConcordanceListInterface {
         "document]article" => "article",
 
         // Book / default
+        "" => "book",
         "buch" => "book",
         "literatur" => "book",
         "document]book" => "book",