<chr_abbr type="frq" class="ss" expan="et" cert="yes">et1</chr_abbr> xx <chr_abbr type="frq" class="ss" expan="et" cert="yes">et1</chr_abbr> xx <chr_abbr type="frq" class="ss" expan="et" cert="yes">et1</chr_abbr> xxx <chr_abbr type="frq" class="ss" expan="et" cert="yes">et1</chr_abbr> xxx. 