Great deal of change over time. Rely on convention over validity?

[seanredmond]

Looking for the simplest format from different volumes, it's clear how much change there is over time, with the earliest volumes being much more complex than the later.

1927 https://archive.org/stream/catalogofcopyrig241libr#page/3/mode/1up

1930 https://archive.org/stream/catalogofcopyri271libr#page/2/mode/1up

1951 https://archive.org/stream/catalogofcopyri351libr#page/402/mode/1up

1962 https://archive.org/stream/catalogofcopyrig3161lib#page/1141/mode/1up

The last one is easy enough (a little different from the current DTD based on some discussions):

<copyrightEntry id="[GUID]" regnum="A578172">
    <author><authorName>ADAMS, O. R.</authorName></author>
    <title>Lameness in horses</title>. © <publisher><pubName claimant="yes">Lea & Febiger</pubName></publisher>;
    <regDate date="1962-08-10">10Aug62</regDate>; <registrationNumber>A578172</registrationNumber>.
</copyrightEntry>

But a definition that works for this and for Rabbit Diseases while accommodating a lot of CDATA punctuation?

I'm leaning towards defining <copyrightEntry> as ANY rather than trying to be really clever about it. It might be more effective to let a program check that everything does indeed have a registration number instead relying on the validity of the XML. We can be more specific in the definition of some of the parts.