Blaabjerg, Ole, Peter Elg, Willie Gerhardt, Kristoffer Hellsing, Elin Olafsdottir, Ilkka Penttilä, Per Hyltoft Petersen, Heidi Steensland, and Adam Uldall. 1993. “6.2.4 A Nordic Reference Serum Suitable for Use As Trueness Control in the Clinical Routine Laboratory”. Upsala Journal of Medical Sciences 98 (3):405-12. https://doi.org/10.3109/03009739309179340.