citation style does not mention " et. al." as promised

[Manoj Rajagopalan]

Hi all,

  In my document, I have inserted a Bibtex bibliography. For certain 
citation items, I choose the "<author> et. al." Citation style from the 
Formatting section of the Citation dialog. This is supposed to give me 
reference of the form "<author> et. al. [ref#] ...". However, when I 
view the DVI I only see text like "[ref#] ..." without the author's name 
as the citation style dialog promises.

  Would anyone know why this is so? I am using the book(AMS) document 
class.

Thanks,
Manoj