\setcounter{enumiv}{9}
would work if the the \thebibliography
wouldn't apply \usecounter{enumiv}
which in turn resets the enumiv
counter.
From article.cls
\newenvironment{thebibliography}[1]
{\section*{\refname}%
\@mkboth{\MakeUppercase\refname}{\MakeUppercase\refname}%
\list{\@biblabel{\@arabic\c@enumiv}}%
{\settowidth\labelwidth{\@biblabel{#1}}%
\leftmargin\labelwidth
\advance\leftmargin\labelsep
\@openbib@code
\usecounter{enumiv}% This is the 'culprit'!!!!!
\let\p@enumiv\@empty
\renewcommand\theenumiv{\@arabic\c@enumiv}}%
\sloppy
\clubpenalty4000
\@clubpenalty \clubpenalty
\widowpenalty4000%
\sfcode`\.\@m}
{\def\@noitemerr
{\@latex@warning{Empty `thebibliography' environment}}%
\endlist}
and from latex.ltx
\def\usecounter#1{\@nmbrlisttrue\def\@listctr{#1}\setcounter{#1}\z@}
i.e. \setcounter{#1}{0}
effectively.
The following code uses a dummy counter mybibstartvalue
and sets the enumiv
counter after \usecounter{enumiv}
using a patch.
However, this code is only meant for article.cls
.
\documentclass{article}
\usepackage{xpatch}
\newcounter{mybibstartvalue}
\setcounter{mybibstartvalue}{9}
\xpatchcmd{\thebibliography}{%
\usecounter{enumiv}%
}{%
\usecounter{enumiv}%
\setcounter{enumiv}{\value{mybibstartvalue}}%
}{}{}
\begin{document}
\cite{Lam94}
\cite{GSM97}
\bibliography{biblio}
\bibliographystyle{unsrt}
\end{document}

\setcounter{enumiv}{9}
, at leastenumiv
is the counter used by thearticle.cls
version of\thebibliography
for the numbering – user31729 Jan 26 '16 at 11:46