Enhancing agricultural innovation : how to go beyond the strengthening of research systems ; [... initiated as a result of the International Workshop Development of Research Systems to Support the Changing Agricultural Sector ... in June 2004 in Washington DC] Why assess the value of the innovation systems perspective The innovation systems concept: a framework for analysis Research methodology and case study descriptions Innovation system capacity: a comparative analysis of case studies Reviewing the innovation systems concept in light of the case studies Towards a framework for diagnosis and intervention