I am experiencing a weird issue in my bibliography.

I have a bibtex entry like:

@online{psqldocs,
author = {PostgreSQL Development Team},
title = "{PostgreSQL Documentation}",
url = {https://www.postgresql.org/docs/}
}


That results in:

[42] PostgreSQL Development Team. PostgreSQL Documentation, . Retrieved
from: https://www.postgresql.org/docs/.


As you can see, there is an extra comma after the title, as bibtex is waiting for the year field. In fact, if I add a year entry for psqldocs, the formatting is ok, having title, year.

How can I fix this? This is a MWE:

\documentclass[13pt, a4paper, titlepage, oneside]{book}
\setcounter{tocdepth}{4}
\setcounter{secnumdepth}{4}
\usepackage[T1]{fontenc}
\usepackage[english]{babel}
\usepackage[latin1]{inputenc}
\usepackage[left=3.00cm, right=3.00cm, top=3.00cm, bottom=3.00cm]{geometry}
\usepackage{setspace}
\renewcommand{\baselinestretch}{1.2}
\usepackage[fontsize=13pt]{scrextend}
\usepackage{xcolor}
\definecolor{wine}{rgb}{0.5,0,0}
\usepackage{hyperref}
\hypersetup{
citecolor = .,
filecolor = .,
runcolor = .,
urlcolor = wine
}
\renewcommand{\UrlFont}{\small}
\usepackage{breakurl}
\usepackage[square,comma,numbers]{natbib}
\bibliographystyle{unsrtnat}
\begin{document}
\cite{psqldocs}
\bibliography{ref}
\end{document}


With ref.bib containing the above bibliography entry.

Please note that, for previous similar entries, I do not see this behavior. For example:

@online{ piezoelectr,
author = "ScienceDirect",
title = "{Piezoelectricity}",
url = "https://www.sciencedirect.com/topics/materials- science/piezoelectricity"
}


results in:

[1] ScienceDirect. Piezoelectricity. Retrieved from:
https://www.sciencedirect.com/topics/materials-science/piezoelectricity.


as expected.

EDIT:

This is the version of the TeX distro I am using (simply obtained inputting pdflatex into my terminal):

This is pdfTeX, Version 3.14159265-2.6-1.40.19 (TeX Live 2018/Arch Linux) (preloaded format=pdflatex)


In addition, I have fixed my MWE. I confirm that I cannot reproduce the described issue. Any clue?

• While the braces and quotes (or double braces) in the title field are debatable (at least in their current WYSIWYG form, I would use title = {{PostgreSQL} Documentation},), you need double braces for the author: author = {{PostgreSQL Development Team}},. See tex.stackexchange.com/q/10808/35864. (Note that I'm not commenting on the issue whether or not your outer field delimiters should be "..." or {...}. I prefer braces, but "..." should work just as well in this example, and with care also in general: tex.stackexchange.com/q/109064/35864) – moewe Feb 26 at 11:16
• If "online" does the job ... why not just use "online". It doesn't seem inappropriate! – Paul Stanley Feb 26 at 11:19
• Mhhh, I stand by my earlier comment, but I just conducted more extensive tests with your MWE and could not reproduce the issue you describe. The entry shows fine as "PostgreSQL Development Team. PostgreSQL Documentation. URL postgresql.org/docs." If you get something different, please double check the MWE and include a picture of the output. – moewe Feb 26 at 11:22

• Load the hyperref package last.

• Since you're loading the setspace package, you have no possible valid excuse for inputting \renewcommand{\baselinestretch}{1.2}. Instead, please input \setstretch{1.2}.

• Instead of [left=3.00cm, right=3.00cm, top=3.00cm, bottom=3.00cm], please just write [margin=3cm].

• Do encase {PostgreSQL Development Team} in an extra pair of curly braces. That way, you signal to BibTeX that it's dealing with a so-called "corporate" author rather than with a person with surname Team, first name PostgreSQL, and middle name Development.

\RequirePackage{filecontents}
\begin{filecontents}{ref.bib}
@online{psqldocs,
author = {{PostgreSQL Development Team}},
title = "{PostgreSQL Documentation}",
url = {https://www.postgresql.org/docs/}
}
@online{ piezoelectr,
author = "ScienceDirect",
title = "{Piezoelectricity}",
url = "https://www.sciencedirect.com/topics/materials- science/piezoelectricity"
}
\end{filecontents}

\documentclass[13pt, a4paper, titlepage, oneside]{book}
\setcounter{tocdepth}{4}
\setcounter{secnumdepth}{4}
\usepackage[T1]{fontenc}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage[margin=3cm]{geometry}
\usepackage{setspace}
\setstretch{1.2}
%\renewcommand{\baselinestretch}{1.2}
\usepackage[fontsize=13pt]{scrextend}
\usepackage{xcolor}
\definecolor{wine}{rgb}{0.5,0,0}

\usepackage[square,comma,numbers]{natbib}
\bibliographystyle{unsrtnat}

\usepackage{url}
\renewcommand{\UrlFont}{\small}

\usepackage{hyperref}
\hypersetup{
citecolor = .,
filecolor = .,

• My bad: adding double braces for author value, the bug does not show up anymore. That's still strange: if I format my PostgreSQL bib entry as the piezoelectr one, I still get the error, while with piezoelectr(and other entries) this issue is completely absent – LucaF Feb 26 at 13:06