引用无法正常工作

Question

我已经为我的文章编写了此代码。

   \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,
    \emph{Advanced Calculus,}
    Jones and Bartlett Publishers, 1990.


\end{thebibliography}
\end{document}

我得到了以下输出。

我该怎么写才不会看起来像[托马斯]，[斯皮瓦克]。我希望它被编号。