# cite is not working properly

I have written this code for my article.

   \documentclass[12pt,a4paper]{amsart}
\renewcommand{\baselinestretch}{1.5}
\textheight 9.3in \textwidth 6.5in \topmargin -1cm
\oddsidemargin-.05cm \evensidemargin -.1cm \topmargin .1cm
\usepackage{amsmath,amsthm,amsfonts,amssymb,amscd}
\usepackage{hyperref}
\usepackage{biblatex}

\begin{document}

\section{Introduction}
This is the reference. \cite{thomas}, \cite{spivak}.
\begin{thebibliography}{}
\bibitem{thomas}
George B. Thomas Jr., Maurice D. Weir, Joel R. Hass
\emph{Thomas' Calculus Early Transcendentals,}
Pearson, 2009.

\bibitem{spivak}
Michael Spivak
\emph{Calculus}
Toronto:
Publish or Perish, Berkeley, 2008.

\bibitem{lumis}
Lynn H. Loomis, Shlomo Sternberg,
Jones and Bartlett Publishers, 1990.

\end{thebibliography}
\end{document}


I am getting the following output.

How will I write so that it will not look like [thomas],[spivak]. I want it to be numbered.

• Don't use biblatex if you want to use \bibitem. – Ulrike Fischer Jul 13 '16 at 21:40
• Either don't use biblatex with biber (the default backend)---use the [backend=bibtex] option for biblatex---or don't use biblatex. – Herb Schulz Jul 13 '16 at 23:23
• Please write up a brief answer showing how you solved the problem. Then accept your answer (there may be a waiting period before you're allowed to). Otherwise, the question will linger as unanswered, and pop up on the front page from time to time. – Harald Hanche-Olsen Jul 14 '16 at 7:56