<texcode>
% LMTX: \tolerant\def\dostartbibitemstartbibitem[#1]#*[#2]%LMTX!
{\doifsomethingelse{#2}%
{\startBibItem[reference={#1},title={#2}]}%
{\startBibItem[reference={#1},title={#1}]}%
}
\def\startbibitem{\dodoubleempty\dostartbibitem}
\def\stopbibitem{\stopBibItem}
% MkIV:
%\def\dostartbibitem[#1][#2]%
% {\doifsomethingelse{#2}%
% {\startBibItem[reference={#1},title={#2}]}%
% {\startBibItem[reference={#1},title={#1}]}%
%}
%\def\startbibitem{\dodoubleempty\dostartbibitem}
%\def\stopbibitem{\stopBibItem}
\definedescription[BibItem][