Stata Corporation <br/><br/>
Stata base reference manual; Q - Z   

 - Texas  Stata Press  2007 
 - V.3 - 635p. 
<br/><br/> "Stata - Release 10"   
<br/><br/><label>ISBN: </label>1597180262 
<br/><br/><label>Dewey Class. No.: </label>518.5425  / St797.SB