F o r t s c h r i t t e d e r C h e m i e d e r P y r r o l e l,70n p r o f . I ) r . -I n g . ha2,II. I V A L T E H S I E I j E T *I iilial t : IV. (:allenEarhstoffe. , V . 1)as Peiitdyopent-Problexii -W. Riedel u. W. FrBwis, Hoppe-Seyler's %. physiol. Cheni. 267, 37 [1940]. ay) W. Yivdrl u. /5. (from, ebenda W , 49 [1940].