GREAT SUCCESS: Research Professor Pernille Rieker (right) and Senior Research Fellow Kristin Haugevik (left) from NUPI chaired a section on differentiated integration at the conference, which took place at Sofia University in September. 'All the panels added to the discussion about differentiated integration. All participants contributed with both empirical analyses across policy fields and the discussion added considerable value to our conceptual understanding of differentiation,' Rieker says.