OPEN University of Sri Lanka <br/><br/>
Course of study leading to the degree of bachelor of science, level 5 PSU 3121-n 

 - Nugegoda  The Open University of Sri Lanka  1990 
 - 62 p. 
<br/><br/><label>ISBN: </label>123720 
<br/><br/><label>Dewey Class. No.: </label>547.71  / OPE