Popkorn, Sally. <br/><br/>
First steps in modal logic / 
Sally Popkorn. 
 - Cambridge :  Cambridge University Press,  1994. 
 - xiii, 314 p. : 
<br/><br/><label>ISBN: </label>052146482X 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Modality (Logic)
<br/><br/><label>Dewey Class. No.: </label>511.3  / Fi