\documentclass[twocolumn,a4paper]{article}
\usepackage{graphicx}
\begin{document}
\title{$\Gamma$-function}
\author{Wikipedia}
\maketitle

\begin{abstract}
In mathematics, the gamma function (represented by $\Gamma$, the capital letter
gamma from the Greek alphabet) is one commonly used extension of the
factorial function to complex numbers.
\end{abstract}

\section{Introduction}

\begin{equation}\label{eq-def}
\Gamma(z) = \int_0^\infty x^{z-1} e^{-x}\,dx, \ \qquad \Re(z) > 0\ .
\end{equation}

Here is a reference to an equation:~(\ref{eq-def}).

\begin{figure}[b]
\includegraphics{gamma_pyx.pdf}
\end{figure}

\begin{figure}[b]
\input{gamma_gnu}
\end{figure}

\end{document}
