\documentclass{article}
\usepackage[latin9]{inputenc}
\usepackage{url}
\usepackage{natbib}
\begin{document}
Test document to verify the BiBTeX database file \texttt{qtfm.bib}
which provides citations for \texttt{QTFM} itself and several articles
and papers which are referenced in the source code.

Note that some of the fields within the BiBTeX database file may not be
printed by the standard BiBTeX style files. In particular, the DOI and
EPRINT fields are not normally output. You should use if possible one of
the style files that supports these fields in order to get a full listing
of the reference. Try, for example, hplain or similar to get the EPRINT
field to print, or the natbib package, used here, which will output the
DOI field.
\nocite{*}
\bibliographystyle{plainnat}
\bibliography{qtfm}
\end{document}