• General syntax for symbols with a kind of lower and upper limits:

\symbolname_{lowerexpression}^{upperexpression}

• In general, there are two ways how these lower and upper expressions can be placed: centered below and above the symbol or in a subscript / superscript manner. In the first case the symbol name is preceded by the word "big", in the second there is no prefix.
• Syntax for the contour integral symbol:

$$\bigoint_{0}^{\infty}$$   gives  

$\bigoint_{0}^{\infty}$

and

$$\oint_{0}^{\infty}$$   gives 

$\oint_{0}^{\infty}$

• Use font size commands for a nicer picture:

$$\LARGE\bigoint_{\small0}^{\small\infty}$$   gives  

$\LARGE\bigoint_{\small0}^{\small\infty}$

and

$$\large\oint_{\small0}^{\small\infty}$$   gives 

$\large\oint_{\small0}^{\small\infty}$