OPEN University of Sri Lanka <br/><br/>
Course of study leading to the degree of bachelor of science, level 5PSU 3122, p 

 - Nugegoda  The Open University of Sri Lanka  1991 
 - 89 p. 
<br/><br/><label>ISBN: </label>123726 
<br/><br/><label>Dewey Class. No.: </label>547.28  / OPE