Validation errors

[baskerville]

I get the following errors when I submit trpl2.epub to epubcheck:

ERROR(RSC-005): trpl2.epub/OEBPS/chapter_013.xhtml(186,17): Error while parsing file 'attribute "start" not allowed here; expected attribute "class", "dir", "id", "lang", "style", "title" or "xml:lang"'.
ERROR(RSC-005): trpl2.epub/OEBPS/chapter_068.xhtml(26,17): Error while parsing file 'attribute "start" not allowed here; expected attribute "class", "dir", "id", "lang", "style", "title" or "xml:lang"'.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_004.xhtml(61,173): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_004.xhtml(80,422): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_004.xhtml(87,313): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_004.xhtml(88,182): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_004.xhtml(97,235): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_004.xhtml(97,422): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_004.xhtml(100,323): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_004.xhtml(316,102): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_020.xhtml(90,353): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_020.xhtml(155,349): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_020.xhtml(184,393): Referenced resource could not be found in the EPUB.
ERROR(RSC-007): trpl2.epub/OEBPS/chapter_028.xhtml(19,173): Referenced resource could not be found in the EPUB.