Sacks, Gerald E. <br/><br/>
Degrees of unsolvability/ 
Gerald E. Sacks. 
 - Princeton, N.J.:  Princeton University Press,  1963. 
 - ix, 174 p.:  24 cm. 
 - Annals of mathematics studies;  55 .
<br/><br/>Bibliography: p. 173-174. 
<br/><br/><label>LCCN: </label>63009996 //r83 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Recursive functions<br/>Unsolvability (Mathematical logic)
<br/><br/><label>Dewey Class. No.: </label>511.3  / S121d