Chellas, B. F. <br/><br/>
Modal logic :  an introduction / 
Brian F. Chellas. 
 - Cambridge :  Cambridge University Press,  1980 
 - xii, 295 p. :  ill. ;  24 cm. 
<br/><br/> Includes bibliographical references and indexes. 
<br/><br/><label>ISBN: </label>0521224764 0521295157 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Modality (Logic)
<br/><br/><label>LC Class. No.: </label>DUCE BC199.M6C47