LaTeX Forum

\usepackage[%
	%round,	%(default) for round parentheses;
	square,	% for square brackets;XXX
	%curly,	% for curly braces;
	%angle,	% for angle brackets;
	%colon,	% (default) to separate multiple citations with colons;
	%comma,	% to use commas as separaters;
	semicolon, % to use semicolons as separaters;XXX
	%authoryear,% (default) for author-year citations;
	numbers,	% for numerical citations;XXX
	%super,	% for superscripted numerical citations, as in Nature;
	%sort,		% orders multiple citations into the sequence in which they appear in the list of references;
	sort&compress,    % as sort but in addition multiple numerical citationsXXX
                   % are compressed if possible (as 3-6, 15);
	%longnamesfirst,  % makes the first citation of any reference the equivalent of
                   % the starred variant (full author list) and subsequent citations
                   %normal (abbreviated list);
	%sectionbib,      % redefines \thebibliography to issue \section* instead of \chapter*;
                   % valid only for classes with a \chapter command;
                   % to be used with the chapterbib package;
	%nonamebreak,     % keeps all the authors names in a citation on one line;
                   %causes overfull hboxes but helps with some hyperref problems.
]{natbib}

%%% Bibliography styles with natbib support
\bibliographystyle{natbib/plainnat.bst} % Numeric Labels, alphabatical order

\usepackage[style=authoryear]{biblatex}

\begin{filecontents}{\jobname.bib}
@Book{schulte-13, 
  title =        {Logistik - Wege zur Optimierung der Supply Chain}, 
  author =       {Schulte, Christof}, 
  year =              {2013}, 
  publisher =    {Vahlen}, 
  adress =          {München}, 
  edition =      {6. Auflage}, 
} 
@Book{schulte-14, 
  title =        {Logistik - Wege zur Verbesserung der Supply Chain}, 
  author =       {Schulte, Christof}, 
  year =              {2014}, 
  publisher =    {Vahlen}, 
  adress =          {München}, 
  edition =      {7. Auflage}, 
} 
\end{filecontents}
\documentclass{scrartcl}
\usepackage[backend=biber, style=authoryear-comp]{biblatex}
\bibliography{\jobname.bib}
\renewcommand{\nameyeardelim}{,~}
\DeclareCiteCommand{\parencite}[\mkbibbrackets]
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{cite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}
\begin{document}
\autocite{schulte-13, schulte-14}
\end{document}