[texhax] problems with sub and super scripts

[M.N.A.Smadi]

Hello there;
couple of things
1) I am trying to write a summation notation as follows:
\sum_{(i,j)\in C(p,q)}

but instead of the {(i,j)\in C(p,q)} showing immediately beneath the big
Sigma notation it shows kind of to the side extending over the term to
be summer over. Any clue how to fix that?

2) i have a variable with a subscript ij and superscript pq. When i use
{x_{ij}}^{pq} , I am getting the x_{ij} as having superscript pq which
is not the same. What is the way around that?

thanks
moe smadi