details"></a></h2>
    <p>A two-step process is used to try to find the requested information. First, a
class-specific function is used (see “Details of the Specialized
Method”).  If this yields nothing, then a general method is used (see
“Details of the General Method”).  If both methods fail, then <code>[[</code>
returns NULL.</p>
<p>Some understanding of the subclass is required to know what can be retrieved
with <code>[[</code>. When dealing with an unfamiliar subclass, it can be useful to
first