File 31-sil-gentium.conf of Package sil-gentium-fonts
<fontconfig>
<alias>
<family>Gentium Basic</family>
<accept>
<family>Gentium Plus</family>
</accept>
</alias>
<alias>
<family>Gentium Book Basic</family>
<accept>
<family>Gentium Book Plus</family>
</accept>
</alias>
</fontconfig>