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% \MRhref is called by the amsart/book/proc definition of \MR.
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\begin{thebibliography}{1}

\bibitem{b}
A.~Browder, \emph{Mathematical analysis}, Undergraduate Texts in Mathematics,
  Springer-Verlag, New York, 1996, An introduction.

\bibitem{r}
W.~Rudin, \emph{Principles of mathematical analysis}, third ed., McGraw-Hill
  Book Co., New York, 1976, International Series in Pure and Applied
  Mathematics.

\end{thebibliography}