Bibliography only shows n.d. instead of the year (Overleaf + pdfLaTeX)

Question

I'm currently writing my thesis, and due to the fact that I already have close to 30 sources, I want to use the vancouver/numeric bibliography style instead of APA. However, I run into some problems when trying to use either of them. Both do not show the year of my bib entries, although they are present in my .bib file.

(APA)

(Vancouver)

(Numeric)

This is the code that is in my main.tex. Please note that I did not write the documentclass or the main myself, I've added things, but I'm not the creator.

\usepackage[
style=apa,
backend=biber,
sortcites=true,
sorting=none,
url=true,
doi=true,
hyperref=false,
backref=false,
natbib=false,
]{biblatex}

\newcommand{\mkbibnodate}{n\adddot d\adddot}
\AtEveryCitekey{\iffieldundef{labelyear}{\restorefield{labelyear}{\mkbibnodate}}{}}
\AtEveryBibitem{\iffieldundef{labelyear}{\restorefield{year}{\mkbibnodate}}{}}

\DeclareLanguageMapping{dutch}{dutch-apa}
\DefineBibliographyStrings{dutch}{andothers = {et al.}}

\addbibresource{bib.bib}
\setlength{\bibitemsep}{1.5 \itemsep}

This is the bib entry that can be seen in the images

@book{kleinwoud_stapersma,
author = {Hans {Klein Woud} and D. Stapersma},
title = {{Design of Propulsion and Electric Power Generation Systems}},
edition = {},
pages = {},
year = {2002},
isbn = {978-1-902536-47-9},
URL = {},
publisher = {IMarEST, Institute of Marine Engineering, Science and Technology}
}

Does anyone know what possibly could lead to this problem, and what I could do to fix this? If I need to proivde any more information, please let me know.

I found this question. The problem here was a missing ,. I checked my .bib, all , and {} are present. I do not have any errors, except a warning that says the ISBN in my bib entry is invalid.

Thanks in advance!

Answer 1

As mentioned in the comments, the problem is indeed your n.d. code. However, if you just delete those lines, then for sources that don't have a date, you won't see n.d. either.

You were looking at labelyear, which isn't used by numeric style, only year is. It is indeed used in apa style, but even there things were going wrong; when labelyear is undefined, which it often is, then year would be used, but you were not checking if year was defined.

Anyway, this should do the trick:

\AtEveryBibitem{
    \iffieldundef{year}{
        \restorefield{year}{\mkbibnodate}
    }{}
}
\AtEveryCitekey{%
    \iffieldundef{year}{%
        \restorefield{year}{\mkbibnodate}%
    }{}%
}

Note the percent signs prevent extra whitespace in your cite brackets. They comment out the newline character at the end of the line, which would else be converted to a space.

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