wro.xml

<groups xmlns="http://www.isdc.ro/wro">
  <group name="wro">
	<css>webjar:bootstrap/3.2.0/less/bootstrap.less</css>   
    <css>file:${project.basedir}/src/main/wro/main.less</css>
    <js>webjar:jquery/2.1.1/jquery.min.js</js>
    <js>webjar:bootstrap/3.2.0/bootstrap.js</js>
  </group>
</groups>