<project [...]>
   <repositories>
		<repository>
			<id>ZK_CE</id>
			<name>ZK CE Repository</name>
			<url>http://mavensync.zkoss.org/maven2</url>
		</repository>
   </repositories>
   <properties>
	<spring.version>3.1.0.RELEASE</spring.version>
	<zk.version>6.0.0</zk.version>
	<zkspring.version>3.1</zkspring.version>
   </properties>
[...]
   <dependencies>
	<dependency>
            <groupId>org.zkoss.zk</groupId>
            <artifactId>zkspring-core</artifactId>
            <version>${zkspring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.zkoss.zk</groupId>
            <artifactId>zkspring-webflow</artifactId>
            <version>${zkspring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.zkoss.zk</groupId>
            <artifactId>zkspring-security</artifactId>
            <version>${zkspring.version}</version>
        </dependency>
   </dependencies>
[...]
</project>

C:\workspace-zk>mvn dependency:tree
[INFO] --------------------------------------------------
[ERROR] BUILD ERROR
[INFO] --------------------------------------------------
[INFO] Failed to resolve artifact.

Missing:
----------
1) org.zkoss.zk:zkspring-core:jar:3.1
[...]
2) org.zkoss.zk:zkspring-webflow:jar:3.1
[...]
3) org.zkoss.zk:zkspring-security:jar:3.1
[...]
[INFO] --------------------------------------------------
C:\workspace-zk>_