\documentclass[12pt]{amsart}
\usepackage{amssymb}
\usepackage{amsmath}

%%%TITLE
\title{XYZ title}
\date{}

%%AFFILIATIONS
\author{John Doe}
\address{University of Knowledge, Street of
Something, Country }
\email{jdone@uknowledge.zz}
\author{Jane Doe}
\address{University of Alternative Knowledgek,  Street
of Something, Country}  
\email{janedoe@science.xx}

%%DOCUMENT
\begin{document}
\maketitle

%%PLEASE PUT YOUR ABSTRACT HERE
\noindent
\textbf{Abstract.}   Please do not use strange packages.
This is a very important article \cite{smith} and \cite{kowalski} a very important book.
This formula is important
\begin{equation}
\int_\omega f,
\end{equation}
where $f$ is a function.
%%THE END OF ABSTRACT

\begin{thebibliography}{99}
\small
\bibitem[1]{kowalski} Kowalski J., On inexistance of strange
options, Cambridge University Press, 2000.

\bibitem[2]{smith} Smith J., \textit{How to add could.} Acta Mathematicae, 268(1), 12012--12312,
2021.
\end{thebibliography}
\end{document}
