Missing \endscname inserted citation

Question

I am new to LaTeX, and I have encountered an error that I couldn't fix myself.

Error: "Missing \endcsname inserted Три \cite{Бідюк2009}"

Неre is a simple document to recreate an error.

\documentclass[a4paper, 14pt, oneside]{report}

\usepackage{extsizes}
\usepackage[utf8]{inputenc}
\usepackage[T1,T2A]{fontenc}
\usepackage[english, russian, ukrainian]{babel}
\usepackage{indentfirst}
\usepackage{misccorr}

\begin{document}
Один \cite{Congdon2006}

Два \cite{Koch2007}

Три \cite{Бідюк2009}
\bibliographystyle{plain}
\bibliography{sources}

\end{document}

The bibliography document (source.bib):

% Encoding: UTF8

@BOOK{Congdon2006,
  title = {Bayesian Statistical Modelling},
  publisher = {John Wiley \& Sons},
  year = {2006},
  author = {Peter Congdon},
  pages = {573},
  edition = {2},
  owner = {Georgii},
  timestamp = {2012.04.01}
}

@BOOK{Koch2007,
  title = {Introduction to Bayesian Statistics},
  publisher = {Berlin: Springer-Verlag},
  year = {2007},
  author = {Karl-Rudolf Koch},
  pages = {249},
  owner = {Georgii},
  timestamp = {2012.04.02}
}

@ARTICLE{Бідюк2009,
  author = {Петро Іванович Бідюк},
  title = {Адаптивне прогнозування фінансово-економічних процесів на основі принципів системного аналізу},
  journal = {Наукові вісті НТУУ КПІ},
  year = {2009},
  volume = {5},
  pages = {54--61},
  owner = {Georgii},
  timestamp = {2012.04.01}
}

Both documents are encoded in UTF-8.

Answer 1

The error is due to the citation key: it's not allowed to use non ASCII characters in them. So change the Бідюк2009 key into Bidjuk2009 or what you prefer.

Use bibtex and not bibtex8, which doesn't support UTF-8, but only 8 bit code pages such as Latin-1. Instead bibtex won't try to interpret any of the character with high bit set.

You should anyway consider switching to biblatex; the problem with citation keys would remain, though.