Index: impl/src/java/org/sakaiproject/citation/impl/BaseCitationService.java
===================================================================
--- impl/src/java/org/sakaiproject/citation/impl/BaseCitationService.java	(revision 53248)
+++ impl/src/java/org/sakaiproject/citation/impl/BaseCitationService.java	(working copy)
@@ -41,6 +41,7 @@
 import java.util.Stack;
 import java.util.TreeSet;
 import java.util.Vector;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.net.URLEncoder;
 
 import org.apache.commons.logging.Log;
@@ -3826,7 +3827,7 @@
 
 	public static final String SCHEMA_PREFIX = "schema.";
 
-	protected static Integer m_nextSerialNumber;
+	protected static AtomicInteger m_nextSerialNumber;
 
 	/*
 	 * RIS MAPPINGS below
@@ -4492,7 +4493,7 @@
 	public void init()
 	{
 		m_storage = newStorage();
-		m_nextSerialNumber = new Integer(0);
+		m_nextSerialNumber = new AtomicInteger(0);
 
 		m_relativeAccessPoint = CitationService.REFERENCE_ROOT;
 
@@ -5195,14 +5196,7 @@
 	 */
 	protected Integer nextSerialNumber()
 	{
-		Integer number;
-		synchronized (m_nextSerialNumber)
-		{
-			number = m_nextSerialNumber;
-			m_nextSerialNumber = new Integer(number.intValue() + 1);
-		}
-
-		return number;
+		return m_nextSerialNumber.getAndIncrement();
 	}
 
 	/*