Read through the following eBooks which are available within Durham University eLibrary (Bookboon):

The Experts Teach: Negotiating Skills

Influencing and Persuasion skills

Negotiation & Assertiveness

If you have difficulty in accessing the eBook you require via the direct link go into Durham University eLibrary (Bookboon) and type the name of the eBook into the search box at the top right hand side of the page.