The MODS documentation for <holdingSimple> describes a subelement
<sublocation>. We just used this element for the first time in preparing
records and found that <sublocation> doesn't actually validate against
http://www.loc.gov/standards/mods/v3/mods-3-4.xsd, but <subLocation> does.
A peak at the 3.4 schema confirms that the sublocation element there does in
fact have a capital "L" in the middle of it! (Presumably an error?)
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