\documentclass[10pt,letterpaper]{article}
\usepackage{natbib}
\begin{document}
\begin{center}\Large{\textbf{Title of the abstract. }}
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Here describe your work. Your submission should not exceed two pages (including all graphs and bibliography). Follow the APA Publication Manual for citation format, both within the text  \citep{reference} and in the reference list. You might need to instal the natbib package. Below is an example reference for a journal article.

 \begin{thebibliography}{apa}
%\bibliographystyle{}
\bibitem[Hill(1983)] {reference} Hill, J. A. C. (1983). A computational model of language acquisition in the two-year old. \emph{Cognition and Brain Theory}, 6, 287-317. 
\end{thebibliography}
\end{document} 