Cassill, Kay. <br/><br/>
Twins :  nature's amazing mystery / 
K. Cassill. 
 - 1st ed. 
 - New York :  Atheneum,  1982. 
 - ix, 308 p. 
<br/><br/> Includes index. 
<br/><br/>Bibliography: p. 279-294. 
<br/><br/><label>ISBN: </label>0689112394 : 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Twins.