# Online citations showing (????) in References in Overleaf

Here is my MWE with all the packages in my complete document.

\begin{filecontents*}{example.eps}
%%BoundingBox: 19 19 221 221
%%CreationDate: Mon Sep 29 1997
%%Creator: programmed by hand (JK)
gsave
newpath
20 20 moveto
20 220 lineto
220 220 lineto
220 20 lineto
closepath
2 setlinewidth
gsave
.4 setgray fill
grestore
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grestore
\end{filecontents*}

\RequirePackage{fix-cm}
\documentclass[twocolumn]{svjour3}
\smartqed
\usepackage{caption}
\usepackage{subcaption}
\usepackage{graphicx}
\usepackage{amsmath}
% \usepackage{amssymb}
\usepackage{float}
\usepackage[sort&compress,numbers]{natbib}
\usepackage{latexsym}
\usepackage{amsfonts}
\usepackage[normalem]{ulem}
\usepackage{soul}
\usepackage{array}
\usepackage{amssymb}
\usepackage{extarrows}
\usepackage{graphicx}
\usepackage{subcaption}
\usepackage{subfig}
\usepackage{wrapfig}
\usepackage{wasysym}
\usepackage{enumitem}
\usepackage{ragged2e}
\usepackage[svgnames,table]{xcolor}
\usepackage{tikz}
\usepackage{longtable}
\usepackage{changepage}
\usepackage{setspace}
\usepackage{hhline}
\usepackage{multicol}
\usepackage{tabto}
\usepackage{float}
\usepackage{multirow}
\usepackage{makecell}
\usepackage{fancyhdr}
\usepackage[table]{xcolor}
\usepackage[toc,page]{appendix}
\tikzset{>={Latex[width=1.5mm,length=2mm]}}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\TabPositions{0.5in,1.0in,1.5in,2.0in,2.5in,3.0in,3.5in,4.0in,4.5in,5.0in,5.5in,6.0in,}
\setcitestyle{numbers,square}
\usepackage[english]{babel}
\usepackage{algorithm2e,algorithmic}
\usepackage[noend]{algpseudocode}

\begin{document}

\section{Introduction}

\label{intro}
This is citation of online web page \cite{online1}. Another online \cite{online2}. Another online \cite{online3}. This is random citation of research papers. \cite{simonyan2014very}. Another paper \cite{he2016deep}
\newline

\bibliographystyle{spbasic_unsort}
\bibliography{reference}
\end{document}
% end of file template.tex



Besides, I am adding the contents of my reference.bib file below.

\usepackage{xurl}

@online{online1,
author = {Collins Online English Dictionary},
title = {Language},
year = {},
url = {https://www.collinsdictionary.com/dictionary/english/language},
urldate = {2021-01-08}
}

@online{online2,
title={Sign Language},
author = {Wikipedia},
url = {https://en.wikipedia.org/wiki/Sign_language},
urldate = {2021-01-08}
}

@online{online3,
title={What is Sign Language?},
author = {David M. Perlmutter },

url = {https://www.linguisticsociety.org/content/what-sign-language},
urldate = {2021-01-08}
}

@article{simonyan2014very,
title={Very deep convolutional networks for large-scale image recognition},
author={Simonyan, Karen and Zisserman, Andrew},
journal={arXiv preprint arXiv:1409.1556},
year={2014}
}

@inproceedings{he2016deep,
title={Deep residual learning for image recognition},
author={He, Kaiming and Zhang, Xiangyu and Ren, Shaoqing and Sun, Jian},
booktitle={Proceedings of the IEEE conference on computer vision and pattern recognition},
pages={770--778},
year={2016}
}



The output looks like that. Notice that, only online references contains (????). I want to remove these question marks.

• @online entries require a year, which then appears in the parantheses. This may be the year, when the website was set up or something like that. I couldn't reproduce the (????) but instead ended up with () when removing the year = xxxx, line from the bibliography though. – Markus G. May 18 at 13:47
• @Markus thanks for your concern but that doesn't solve my full problem. I think the problem lies in the packages. I may need to import or remove some packages but couldn't conclude anything for sure. – Nieb_Hasan_077 May 18 at 13:59
• However, you do realise that either year or date (but not urldate) is required(!) for @online-type entries? I am referring to this answer: tex.stackexchange.com/a/263912/118712 – Markus G. May 18 at 14:02
• @MarkusG. no, I didn't know that year or date is mandatory. I think I know how to proceed further with my document. Sometimes little knowledge can solve big problems (or seem to be big). Thanks for the information. – Nieb_Hasan_077 May 19 at 5:51