%&LaTeX
\documentclass{article}

\usepackage[latin1]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{textcomp}

\begin{document}

\begin{thebibliography}{1}

\bibitem{Aytas_etal1999} Aytas, S. O., Akyil, S., Aslani, M. A. A., \& Aytekin, U. (1999). Removal of uranium from aqueous solutions by diatomite (Kieselguhr). \textit{Journal of Radioanalytical and Nuclear Chemistry}, \textit{240}(3), 973--976.

\end{thebibliography}

\end{document}

