\documentclass{article}

\usepackage{amssymb,amsmath,amsfonts}

\newcounter{nonumber}
\renewcommand{\thenonumber}{}
\newtheorem{theorem}[nonumber]{Theorem}

\begin{document}

\begin{center}
{\large \textbf{Title of the talk}}\\[2mm]
\textbf{Author}\\
University, Country\\[2mm]
(Joint work with ... (coauthors))\\[2mm]
Address\\
E-mail
\end{center}

Abstract of the talk. Please do not use your own macros. If
necessary, you can add extra packages. Theorems can be stated as
follows.

\begin{theorem}
Main result.
\end{theorem}

Please do not use the bibliography environment. References can be
included in the following way~[1].

\bigskip

\noindent\textbf{References}
\begin{description}
\item[{[1]}] Author, \emph{Title}, Journal \textbf{17} (2015), 101--112.
\end{description}

\end{document}
