A, then E, then B, then D, and then again E

I have just completed an ultra short letter to JACI on a confusing vitamin D article Good to know that even the beginning of the field is marked by a highly confusing nomenclature. As you can see from the paper of E. v. Hahn [Zschr f Unters d Lebensm 1930;59:5] the rickets-vitamin was first called A, then E, then B, then D and then again E.