引文在输入时未定义，即使它们存在

Question

Hi I'm using Overleaf for my dissertation and this warning started popping up recently: Citation 'objprogen' on page 1 undefined on input line 8.

This citation is already created as seen below in the 'sources.bib' file:

@article{objprogen,
  author={Guo, Wenzhong and Lin, Renjie and Wang, Shiping and Xiong, Neal},
  booktitle={2018 9th International Symposium on Parallel Architectures, Algorithms and 
  Programming (PAAP)}, 
  title={Object Proposal Generation for Unsupervised Object Localization}, 
  year={2018},
  volume={},
  number={},
  pages={235-242},
  doi={10.1109/PAAP.2018.00046}}

This is my main.tex file:

\documentclass[a4paper]{article}
\usepackage{blindtext, graphicx}
\usepackage{csquotes}
\usepackage[hidelinks]{hyperref}
\usepackage{url}
\usepackage[style=authoryear-ibid,backend=biber]{biblatex}
\hyphenation{op-tical net-works semi-conduc-tor}
\bibliography{sources.bib}

\begin{document}

\title{Can image recognition systems be successfully integrated with existing VIN databases 
irrespective of the vehicle manufacturer}
\author{myname}


\maketitle{}

\input{includes/01-Abstract}
\input{includes/02-Introduction}
\input{includes/03-Literature}
\input{includes/04-Methodology}
\input{includes/05-Findings}
\input{includes/06-Conclusion}
\input{includes/07-Appendix}

\end{document}

Answer 1

I had the same problem and solved it by adding \bibliographystyle{plain} (of course you could in principle use other styles). For me the structure of the tex file is the following

\documentclass[oneside, a4paper, onecolumn, 11pt]{article}
%%some packages%%
\begin{document}
%%% some stuff

\bibliographystyle{plain}
\bibliography{bibfile} %bibfile name without the .bib extension

\end{document}

So contrary to you the \bibliography is also inside the document environment.