Petrich, Mario <br/><br/>
Rings and semigroups   

 - Berlin  Springer-Verlag  1974 
 - viii, 182p. 
 - Lecture notes in Mathematics   380 .
<br/><br/> "Appendix by Richard Wiegandt"   
<br/><br/><label>Dewey Class. No.: </label>512  / P495.RS