Döös, M., Wilhelmson, L., Madestam, J. and Örnberg, Åsa 2018. The Principle of Singularity: A Retrospective Study of How and Why the Legislation Process behind Sweden’s Education Act came to Prohibit Joint Leadership for Principals. Nordic Journal of Comparative and International Education (NJCIE). 2, 2-3 (Nov. 2018), 39–55. DOI:https://doi.org/10.7577/njcie.2757.