diff --git a/pom.xml b/pom.xml
index 5e45e318c..cd84cd7f7 100644
--- a/pom.xml
+++ b/pom.xml
@@ -61,17 +61,17 @@
     <developer>
       <id>jwayman</id>
       <name>Jeff Wayman</name>
-      <email></email>
+      <email/>
     </developer>
     <developer>
       <id>dcowden</id>
       <name>Dave Cowden</name>
-      <email></email>
+      <email/>
     </developer>
     <developer>
       <id>lawson89</id>
       <name>Richard Lawson</name>
-      <email></email>
+      <email/>
     </developer>
     <developer>
       <id>dougmorato</id>
@@ -111,7 +111,7 @@
     <!-- Shared properties with plugins and version numbers across submodules-->
     <asciidoctorj.version>2.5.10</asciidoctorj.version>
     <!-- Upgrading needs UI work in WebWolf -->
-    <bootstrap.version>3.3.7</bootstrap.version>
+    <bootstrap.version>4.0.0</bootstrap.version>
     <cglib.version>3.3.0</cglib.version>
     <!-- do not update necessary for lesson -->
     <checkstyle.version>3.3.0</checkstyle.version>
@@ -539,8 +539,8 @@
               <includes>
                 <include>.gitignore</include>
               </includes>
-              <trimTrailingWhitespace></trimTrailingWhitespace>
-              <endWithNewline></endWithNewline>
+              <trimTrailingWhitespace/>
+              <endWithNewline/>
               <indent>
                 <tabs>true</tabs>
                 <spacesPerTab>4</spacesPerTab>
@@ -551,7 +551,7 @@
             <includes>
               <include>**/*.md</include>
             </includes>
-            <flexmark></flexmark>
+            <flexmark/>
           </markdown>
           <java>
             <includes>
@@ -559,7 +559,7 @@
               <include>src/test/java/**/*.java</include>
               <include>src/it/java/**/*.java</include>
             </includes>
-            <removeUnusedImports></removeUnusedImports>
+            <removeUnusedImports/>
             <googleJavaFormat>
               <style>GOOGLE</style>
               <reflowLongStrings>true</reflowLongStrings>