Getting to yes
Roger Fisher and William Ury; Penguin Books. This book is the first of a trilogy, which offers a practical, universally applicable approach for coming to mutually acceptable agreements in disputes ranging from domestic conflict, business disputes, and international tensions.
Getting Past No
William Ury; Bantam Books. This book offers strategies for dealing with someone who is angry, unreasonable, deceitful, or stubborn and does not want to negotiate.