xmllint is a useful tool to use to check your XML files. Sometimes publican build will give you an error that may be difficult to interpret. xmllint's parser can give more accurate details as to the location of the error and also can give you a description that makes more sense to a human. Another advantage to xmllint is that it can process a single XML file whereas publican build must parse the entire book. The xmllint package can be installed using the yum install xmllint as follows:

# yum install xmllint.

xmllint name-of-file