The first resource on integrative negotiation, positions and interests should be William Ury, Roger Fisher and Bruce Patton’s classic Getting to Yes: Negotiating Agreement without Giving In.  A close second would be Ury’s sequel Getting Past No: Negotiating in Difficult Situations.  I strongly recommend these two books to the professional library of every negotiator.

Free online explanations of interests and positions are plentiful and can be found with a search.  Among the better articles I came across are these by Cinnie Noble, the University of Colorado Boulder, the U.S. Institute of Peace, and Watershed Associates; I liked the latter’s many helpful charts.  Note the ubiquity of the orange story (and the lack of citation of it — if only I knew who originated it!).