%
% This example demonstrates how hybrid citations, i.e., two
% citations styles in a single document, may be implemented.
% Note that the default styles which ship with bibatex do not
% support hybrid citation schemes out of the box. This example
% is merely a proof of concept.
%
\documentclass[a4paper,oneside]{article}
\usepackage[T1]{fontenc}
\usepackage[american]{babel}
\usepackage[utf8]{inputenc}
\usepackage{csquotes}
% We use the authoryear style as a basis but we want numerical
% labels for all online references. Therefore, we request numeric
% labels by setting 'labelnumber=true'. We also set
% 'defernumbers=true'. This will be required by the 'omitnumbers'
% option used below.
\usepackage[style=authoryear,labelnumber,defernumbers,backend=biber]{biblatex}
\usepackage{hyperref}
\usepackage{nameref}
\addbibresource{biblatex-examples.bib}

% We define a dedicated citation command for online references which
% uses numerical labels instead of the author-year scheme. Instead
% of defining a dedicated command, it is also possible (and usually
% preferable) to build smart citation commands which are able to
% switch citation styles depending on the entry type (or other
% criteria). It's just easier to demonstrate the point of the
% 'omitnumbers' option this way:

\DeclareCiteCommand{\citeonline}[\mkbibbrackets]
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \printtext[bibhyperref]{%
     \printfield{labelprefix}%
     \printfield{labelnumber}}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

% The matching environment for the online sub-bibliography:

\defbibenvironment{online}
  {\list
     {\printtext[labelnumberwidth]{%
	\iffieldundef{shorthand}
	  {\printfield{labelprefix}%
	   \printfield{labelnumber}}
	  {\printfield{shorthand}}}}
     {\setlength{\labelwidth}{\labelnumberwidth}%
      \setlength{\leftmargin}{\labelwidth}%
      \setlength{\labelsep}{\biblabelsep}%
      \addtolength{\leftmargin}{\labelsep}%
      \setlength{\itemsep}{\bibitemsep}%
      \setlength{\parsep}{\bibparsep}}%
      \renewcommand*{\makelabel}[1]{\hss##1}}
  {\endlist}
  {\item}

\DeclareFieldFormat{labelnumberwidth}{\mkbibbrackets{#1}}

\begin{document}

\section*{Hybrid citations}

\subsection*{Regular citations (author-year)}

\cite{augustine},
\cite{bertram},
\cite{companion}

\subsection*{Online citations (numeric)}

\citeonline{ctan},
\citeonline{markey}

% Let's print the overall heading of the bibliography first:
\printbibheading

% We set omitnumbers=true for the author-year sub-bibliography.
% Without that, the first item of the online bibliography would be
% labeled as "[4]".
\printbibliography[heading=subbibliography,title={Printed References},nottype=online,omitnumbers]

% The online sub-bibliography requires a different environment:
\printbibliography[heading=subbibliography,title={Online References},env=online,type=online]

\end{document}
