Error `Missing \endcsname inserted` (Bibliography, bibtex)

Question

While adding references in my thesis paper, I copied the following BibTex from google scholar:

    @article{aygunoǧlu2009introduction,
  title={Introduction to fuzzy soft groups},
  author={Ayg{\"u}noǧlu, Abd{\"u}lkadir and Ayg{\"u}n, Halis},
  journal={Computers \& Mathematics with Applications},
  volume={58},
  number={6},
  pages={1279--1286},
  year={2009},
  publisher={Elsevier}
}

After pasting the same in the .bib file which I created, I added the label key in the original .tex file. But I am getting the following error:

line 52: Missing \endcsname inserted. ...on 2.15} \cite{aygunoǧlu2009introduction}

Please suggest me how to fix it.

Answer 1

The citation keys should not have special characters: sticking to letters (without accents) and digits is best.

You could have aygunoǧlu2009introduction if you compile with XeLaTeX or LuaLaTeX, but the bib file would not be really portable.

So the best solution is to change the key from

aygunoǧlu2009introduction

to

aygunoglu2009introduction

If you compile with pdflatex it's also better to change the author name to

Ayg{\"u}no{\u{g}}lu

so sorting will not give problems.