Generation and Characterization of Six Recombinant Botulinum Neurotoxins as Reference Material to Serve in an International Proficiency Test., Weisemann, Jasmin, Krez Nadja, Fiebig Uwe, Worbs Sylvia, Skiba Martin, Endermann Tanja, Dorner Martin B., Bergström Tomas, Muñoz Amalia, Zegers Ingrid, et al. , Toxins (Basel), 2015 Nov 26, Volume 7, Issue 12, p.5035-54, (2015)