Robert Benewick & Philip Green 
The Routledge Dictionary of Twentieth-Century Political Thinkers [PDF ebook] 

This edition has been revised and extended to include eleven new entries on Berlin, Chomsky, Derrida, Rorty and many others. Key features of this unique guide include:
* 170 entries from 96 contributors, many of whom are leading authorities in their field
* alphabetically arranged entries which include brief biographies, outlines of major ideas and suggestions for further reading
* coverage of Western and Third World political theorists as well as those who have influenced new movements based on the issues of ethnicity, gender and ecology
* a thematically organised index