当语言包含在 @book 中时，revtex4 会出现书目错误

Question

当我尝试编译引用.bib 中的以下条目的 Latex 文档时：

@book{a_book,
    title = {A Book},
    publisher = {Book Publisher},
    author = {Fist, Last},
    year = {2015},
    language = {en},
}

我收到以下两个错误：

Package babel Error: You haven't defined the language en yet.
Package babel Error: You haven't loaded the language english yet.

当我从 BibTex 条目中删除时，一切都正常language = {en}。但是，此行包含在@article条目中且没有错误。

发生了什么事？为什么包含此行只会导致条目出错@book？

版本信息：

This is BibTeX, Version 0.99d (TeX Live 2013)
This is pdfTeX, Version 3.1415926-2.5-1.40.14 (TeX Live 2013)

测试文件：

测试.tex

\documentclass{revtex4-1}

\begin{document}
This is an article. \cite{an_article}.

This is a book \cite{a_book}.   

\bibliographystyle{apsrev4-1}
\bibliography{test}

\end{document}

测试文件

@book{a_book,
 title = {A Book},
 publisher = {Book Publisher},
 author = {Last, First},
 year = {2015},
 language = {en},
}

@article{an_article,
 title = {An Article},
 volume = {1},
 number = {1},
 journal = {Journal},
 author = {Last, First},
 year = {2015},
 pages = {1-10},
 language = {en},
}

Answer 1

当您language在 bib 条目中有一个字段时，您需要babel为所需的所有语言加载适当的语言选项。最后指定的选项将是默认值。

但是，language={en}会导致文件\selectlanguage{en}中出现无法理解的字符。尽管如此，我们可以稍微扩展一下，让它使用语言别名。在我看来，这将是一个不错的功能，而且实现起来并不困难。.bblbabelbabelbabel

\begin{filecontents*}{\jobname.bib}
@book{a_book,
 title = {A Book},
 publisher = {Book Publisher},
 author = {Last, First},
 year = {2015},
 language = {en},
}

@article{an_article,
 title = {An Article},
 volume = {1},
 number = {1},
 journal = {Journal},
 author = {Last, First},
 year = {2015},
 pages = {1-10},
 language = {en},
}
\end{filecontents*}

\documentclass{revtex4-1}
\usepackage[english]{babel}

\makeatletter
% A change to a babel macro
\def\bbl@set@language#1{%
  \edef\languagename{%
    \ifnum\escapechar=\expandafter`\string#1\@empty
    \else\string#1\@empty\fi}%
  %%%% ADDITION
  \@ifundefined{babel@language@alias@\languagename}{}{%
    \edef\languagename{\@nameuse{babel@language@alias@\languagename}}%
  }%
  %%%% END ADDITION
  \select@language{\languagename}%
  \expandafter\ifx\csname date\languagename\endcsname\relax\else
    \if@filesw
      \protected@write\@auxout{}{\string\select@language{\languagename}}%
      \bbl@for\bbl@tempa\BabelContentsFiles{%
        \addtocontents{\bbl@tempa}{\xstring\select@language{\languagename}}}%
      \bbl@usehooks{write}{}%
    \fi
  \fi}
% The user interface
\newcommand{\DeclareLanguageAlias}[2]{%
  \global\@namedef{babel@language@alias@#1}{#2}%
}
\makeatother

\DeclareLanguageAlias{en}{english}

\begin{document}
This is an article. \cite{an_article}.

This is a book \cite{a_book}.   

\bibliographystyle{apsrev4-1}
\bibliography{\jobname}

\end{document}