Originally Posted by

**ENRIQUESTEFANINI** Hi:

I am sending the whole text bellow:

'and [LaTeX ERROR: Unknown error] , ' should be replaced by 'and MATH_TAG \{ \} /MATH_TAG, '

Hi:

In the book The Theory of Finite Groups: An Introduction, by Hans Kurzweil and Bernd Stellmacher, New York, 2004, in section 1.6, Products of Groups, there is Exercise 3:

Let $\displaystyle G$ be finite. Suppose that every maximal subgroup of $\displaystyle G$ is simple and normal in $\displaystyle G$. Then $\displaystyle G$ is an Abelian group and $\displaystyle \{ \} $, where $\displaystyle p, q$ are primes.

END OF TEXT

Would you be so nice to tell me what to do?

EDIT

More simple than that: the following text:

]MATH[ \{ ]MATH[

causes LaTeX ERROR: Unknown error. I wrote inverted square brackets on purpose, only here.