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

\symbolname_{<em>lowerexpression</em>}^{<em>upperexpression</em>}

• 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 integral symbol:

$$$\bigint_{0}^{\infty}$$$   gives  

$$\bigint_{0}^{\infty}$$

and

$$$\int_{0}^{\infty}$$$   gives 

$$\int_{0}^{\infty}$$

• Use font size commands for a nicer picture:

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

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

and

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

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