Epub Errors? about epubcheck HOT 2 CLOSED

The leading errors are:

ERROR: With God in Russia - Ciszek_ Fr. Walter.epub/content.opf(2): bad value 
for attribute "unique-identifier"
ERROR: With God in Russia - Ciszek_ Fr. Walter.epub/content.opf(2): 
unique-identifier attribute in package element must be present and have a value
ERROR: With God in Russia - Ciszek_ Fr. Walter.epub/content.opf: 
unique-identifier attribute in package element must reference an existing 
identifier element id
ERROR: With God in Russia - Ciszek_ Fr. 
Walter.epub/With_God_in_Russia_split_3.html(12): element "span" from namespace 
"http://www.w3.org/1999/xhtml" not allowed in this context
ERROR: With God in Russia - Ciszek_ Fr. 
Walter.epub/With_God_in_Russia_split_3.html(12): unfinished element

The first three are due to:

<package xmlns="http://www.idpf.org/2007/opf" version="2.0" 
unique-identifier="">

The unique-identifier can't have an empty value -- in this case it probably 
wants to be "calibre-uuid".  Which would correctly point to a <dc:identifier>.

The rest of the errors seem to be the likes of:

<blockquote><span>foo</span></blockquote>

<blockquote> may only contain other block-level elements (e.g. <p>s), <span> is 
an inline element and, thus not allowed in this context.