My bibtex file has approximately 15 books but only 10 of them are
shown in the pdf file. Please what could I do in order to have all of
them shown?
\bibliographystyle{plain}
\bibliography{bibs/references}
Something that I think can happen is if there is a mistake in the
argument to \bibliography{}, bibtex will stop processing at that
point. Say for instance I have the line:
\bibliography{../abc,../def,../ghi,../jkl}
Everything is fine with ../abc.bib, but ../def.bib is missing
or perhaps seriously flawed. bibtex will enter the ones it
has found, and stop, so those from ../ghi.bib and ../jkl.bib
do not appear in the output either.
I don't know if that's the case in your document, but it's
something to look at. Also, BibTeX files seem to me to be
notorously sensitive to booboos (rightfully so, I'm sure),
so if you forget a comma or have a duplicate key or something,
things just don't work right.