Heading over the first column (the term column) of a definition list (two-part list)
<!ELEMENT term-head (#PCDATA %def-list-head-elements;)* >
Any combination of:
...
<def-list>
<title>ABBREVIATIONS</title>
<term-head>Expansion</term-head>
<def-head>Abbreviation</def-head>
<def-item><term id="G1">PAP I</term>
<def><p>poly(A)polymerase I</p></def>
</def-item>
<def-item><term id="G2">PNPase</term>
<def><p>polynucleotide phosphorylase</p></def>
</def-item>
<def-item>...</def-item>
...
</def-list>
...
list.ent