Can't download certain type of artifacts

[Cao, Lili (NSN - CN/Hangzhou)]

Hi,
  I encounter issue that ivy can only download jar files from repository, but 
can't download other type of artifacts, could you please help checking the 
issue?

  Here is what I defined in properties file:
      
ivy.default.ivy.pattern=[orgPath]/[module]/[branch]/[revision]/[type]/ivy_${component}.xml
  
ivy.default.artifact.pattern=[orgPath]/[module]/[branch]/[revision]/[type]/[artifact].[ext]

 Here is used in ivysettings.xml
                                <url name="httpResolver" >
                     <ivy
                            
pattern="http://${ivy.nexus.server}/nexus/content/repositories/${ivy.default.ivy.pattern}";
                           />
                     <artifact
                            
pattern="http://${ivy.nexus.server}/nexus/content/repositories/${ivy.default.artifact.pattern}";
                           />
              </url>

I defined two types for artifacts:
<artifact name="a" type="jar" ext="jar"/>
      <artifact name="a_changes" type="readme" ext="html"/>

Here is publish and download part:
<target name="publish_artifacts"  depends="set_ivy_settings" 
description="publish artifacts to repository. this target is only for testing. 
we need do this during promotion.">
              <ivy:publish  pubrevision="${build_version}"  
resolver="httpResolver" update="true" overwrite="true">
              <artifacts pattern="${output.dir}/[artifact].[ext]" />
              <artifacts pattern="${output.dir}/jar/[artifact].[ext]"/>
              <artifacts pattern="${output.dir}/readme/[artifact].[ext]"/>
       </ivy:publish>
       </target>
   <target name="download_artifacts" description="download artifacts of 
dependent components." depends="ivy_file_resolve">
              <ivy:retrieve pattern="${artifacts.dir}/[type]/[artifact].[ext]" 
type="jar,readme"/>
   </target>


I can publish artifacts correctly in my repository, but only jar files download 
to local, readme files can't be downloaded, could you please help on this? 
Which part might be wrong?  Thanks!

Br,
Lillian