将引用样式改为 Doe, J. (2013a)，而不是 Doe, J. (2013)a

Question

我目前正在寻找一种方法来调整引用样式以适应我所在大学的要求。目前，当存在多本具有相同作者和年份的书籍时，我会得到脚注See John, D. (2013)a。我该如何更改它，以便将字母放在括号内？

编辑：这里是最小的例子：

\documentclass[12pt, a4paper]{scrartcl}
\usepackage[citestyle=dhbw_ibim]{biblatex}
\bibliography{bibliography}
\begin{document}
foo\footcite[See][2]{test1}
bar\footcite[See][5]{test2}
\end{document}

citestyle 文件可从以下位置获取：https://github.com/schocco/DHBW-stgt-template/blob/master/src/dhbw_ibim.cbx

所用围兜为：

@misc{test1,
author = {Doe, John},
year = {2013}
} 

@misc{test2,
author = {Doe, John},
year = {2013}
} 

最后，我使用以下命令进行编译：

pdflatex mini.tex | biber mini | pdflatex mini.tex

编辑2：\listfiles

*File List*
scrartcl.cls    2012/07/29 v3.11b KOMA-Script document class (article)
scrkbase.sty    2012/07/29 v3.11b KOMA-Script package (KOMA-Script-dependent basics and keyval usage)
scrbase.sty    2012/07/29 v3.11b KOMA-Script package (KOMA-Script-independent basics and keyval usage)
keyval.sty    1999/03/16 v1.13 key=value parser (DPC)
scrlfile.sty    2012/06/15 v3.12 KOMA-Script package (loading files)
tocbasic.sty    2012/04/04 v3.10b KOMA-Script package (handling toc-files)
scrsize12pt.clo    2012/07/29 v3.11b KOMA-Script font size class option (12pt)
typearea.sty    2012/07/29 v3.11b KOMA-Script package (type area)
biblatex.sty    2013/07/15 v2.7a programmable bibliographies (PK/JW/AB)
biblatex2.sty    2013/07/15 v2.7a programmable bibliographies (biber) (PK/JW/AB)
etoolbox.sty    2011/01/03 v2.1 e-TeX tools for LaTeX
etex.sty    1998/03/26 v2.0 eTeX basic definition package (PEB)
kvoptions.sty    2011/06/30 v3.11 Key value format for package options (HO)
ltxcmds.sty    2011/11/09 v1.22 LaTeX kernel commands for general use (HO)
kvsetkeys.sty    2012/04/25 v1.16 Key value parser (HO)
infwarerr.sty    2010/04/08 v1.3 Providing info/warning/error messages (HO)
etexcmds.sty    2011/02/16 v1.5 Avoid name clashes with e-TeX commands (HO)
ifluatex.sty    2010/03/01 v1.3 Provides the ifluatex switch (HO)
logreq.sty    2010/08/04 v1.0 xml request logger
logreq.def    2010/08/04 v1.0 logreq spec v1.0
ifthen.sty    2001/05/26 v1.1c Standard LaTeX ifthen package (DPC)
url.sty    2006/04/12  ver 3.3  Verb mode for urls, etc.
blx-dm.def
dhbw_ibim.dbx
biblatex-dm.cfg
blx-compat.def    2013/07/15 v2.7a biblatex compatibility (PK/JW/AB)
biblatex.def
standard.bbx    2013/07/15 v2.7a biblatex bibliography style (PK/JW/AB)
numeric.bbx    2013/07/15 v2.7a biblatex bibliography style (PK/JW/AB)
dhbw_ibim.cbx    2013/07/15 v2.7a biblatex citation style (PK/JW/AB)$Id:dhbw_ibim.cbx,v 0.1 2011/06/08 Rocco Schulz $
biblatex.cfg
english.lbx    2013/07/15 v2.7a biblatex localization (PK/JW/AB)
mini.bbl

提前致谢！