chicago.bst ファイルの年の前にドット (.) を追加するにはどうすればよいですか?

Question

chicago.bst ファイルの年 (2012) の前にドット (.) を追加する方法 (以下のように)

Bergmann, H. および U. Stephan (2012)。「初期の起業家精神から脱却する：新しい事業所有権への移行における国際的差異の測定」Small Business Economics 41:945-959。

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以下にBIBエントリを追加しました

@article{bs12,
author = {Bergmann, H. and U. Stephan},
title = {Moving on from nascent entrepreneurship: measuring cross-national 
         differences in the transition to new business ownership},
journal = {Small Business Economics},
volume = {41},
year = {2012},
pages = {945-959},
}

@article{bs12,
author = {Bergmann, H. and U. Stephan},
title = {Moving on from nascent entrepreneurship: measuring cross-national differences in the transition to new business ownership},
journal = {Small Business Economics},
volume = {41},
year = {2012},
pages = {945-959},
}

@ARTICLE{bgk10,
author = {Brinckmann, J. and D. Grichnik and D. Kapsa},
title = {Should entrepreneurs plan or just storm the castle? {A} meta-analysis on contextual factors impacrting the business planning-performance relationship in small firms},
journal = {Journal of Business Venturing},
volume = {25},
year = {2010},
pages = {24-40},
}

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 \documentclass[openany]{now}
   \begin{document}

   \nocite{*}
   \bibliographystyle{chicago}
   \bibliography{sample-bib}
   \end{document}