Errors with AMS documentclass

[Wang Yongqiao]

I am writing a book with AMS book document.    When I convert it to dvi or pdf, 
the following erros are found:

LaTeX Error: No counter 'thm' defined.
LaTeX Error: No counter 'thm' defined.
LaTeX Error: Environment defn undefined.
LaTeX Error: \begin{document} ended by \end{defn}.

Can you tell how to handle this problem?        

　　　　　　　　Wang Yongqiao
[EMAIL PROTECTED]
　　　　　　　　　　2007-11-26