\documentclass[twoside]{mfa}
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%\usepackage{geometry}
%\geometry{paperheight=25cm,paperwidth=17.6cm,inner=25.5mm,top=32mm,textwidth=12.5cm,textheight=19.7cm}
\usepackage{amssymb,amsfonts}
\renewcommand\volume{{\bf 8} (2019)} %% volume
%\setcounter{page}{3}
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%%% Additional packages %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{graphicx}
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\newcommand\refrm[1]{{\rm (\ref{#1})}}
\newcommand\bbreak{\allowdisplaybreaks}
\newcommand\dd{\mathop{\rm d\!}\nolimits}
\newcommand\sgn{\mathop{\rm sgn}\nolimits}
\newcommand\dx[1]{\mathrm{d}#1}
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\begin{document}
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%% title page %%
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\title[(Shortened title]{TITLE TITLE TITLE}
\author[F1. Surname1]{Forename1 Surname1}
\address{Department of ..., University ..., Address ...}
\email{xxx@xxx.xx}
%\curraddr{}
%\urladdress{http://www.anonymous.com/anonymous/index.html}
\author[F2. Surname2]{Forename2 Surname2}
\address{Department of ..., University ..., Address ...}
\email{xxx@xxx.xx}
%\dedicatory{Dedicated to ...}
\thanks{The research was supported ...}
%%%%%%%% Keywords %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\keywords{keyword 1, keyword 2}
%%%%%%%% AMS classification 2010 %%%%%%%%%%%%%%%%%%%%%%%%
\subjclass{34K06, 34K25}{39} %% \subjclass{primary}{secondary}
%%%%%%%% Abstract %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{abstract}
Abstract abstract abstract abstract abstract abstract abstract abstract abstract.
\end{abstract}
%%%%%%%% Environments Theorem, Definition, etc. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\newtheorem{theorem}{Theorem}[section]
\newtheorem{corollary}[theorem]{Corollary}
\newtheorem{lemma}[theorem]{Lemma}
\newtheorem{proposition}[theorem]{Proposition}
\theoremstyle{definition}
\newtheorem{definition}[theorem]{Definition}
\newtheorem{problem}[theorem]{Problem}
\newtheorem{example}[theorem]{Example}
\newtheorem{remark}[theorem]{Remark}
%\theoremstyle{remark}
%\newtheorem{remark}[theorem]{Remark}
\numberwithin{equation}{section}
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\maketitle
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%% Article body %%
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\section{Introduction}
Text text text text text text.
\begin{align}
f(x)=\dots
\end{align}
\begin{theorem} Theorem-like environments.
\end{theorem}
\begin{proof} Proof of Theorem ...
\end{proof}
Text text text text text text.
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%% References %%
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\begin{thebibliography}{99}
\bibitem{Baker}
C.\,T.\,H. Baker, {\em Retarded differential equations}, Journal of Computational and Applied Mathematics {\bf 125} (2000), 309--335.
\bibitem{Erbe}
L.\,H. Erbe, Q. Kong and B.\,G. Zhang,
{\em Oscillation Theory for Functional Differential Equations}, Marcel Dekker, New York, 1995.
\bibitem{NovakRuricha}
F. Novak and L. Ruricha, {\em Theory of nothing}, in: Proceedings of the 4th Prague Int. Conference on Theory of Nothing, Kluwer, Dordrecht, 2011, 176--189.
\end{thebibliography}
\end{document}
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