[1] choose - MDC (1/21/2010, 4:29:14 AM 版) <https://developer.mozilla.org/en/XPath/Functions/choose>
[2] XProc 2.0: An XML Pipeline Language (7/21/2016, 5:35:49 AM) <https://www.w3.org/TR/2016/NOTE-xproc20-20160721/#p.choose>
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