How to download sources for a jar with Maven?

In my project I am using a JAR file provided via Maven. But what Maven gives me is only this jar - no javadocs and no sources. Pressing "Download Sources" has no effect: Eclipse still does not find the sources of the jar.

What this depends on? Should repository provide sources automatically?

May be I need to write something in POM to instruct Maven to download sources?

My current pom follows:

<repositories>
    <repository>
        <id>xuggle repo</id>
        <url>http://xuggle.googlecode.com/svn/trunk/repo/share/java/</url>
    </repository>
</repositories>

<dependencies>

    <dependency>
        <groupId>xuggle</groupId>
        <artifactId>xuggle-xuggler</artifactId>
        <version>5.3</version>
        <type>rar</type>
    </dependency>

</dependencies>

Why Maven does not say any comments on it's sources download fail?