see \cite{aaaaa}

\begin{thebibliography}{9} 
    
\bibitem{aaaaa}Amer. Math. Soc., Providence, RI, 
    1994; distributed with the AMSFonts package.

\bibitem{bbbbb}Amer. Math. Soc., Providence, RI, 
    1995; distributed with the AMSFonts package.

\end{thebibliography}