1. P. Karrer and E. Jucker, Carotinoide (Birkhäuser, Basle 1948); English translation by E. A. Braude (Elsevier, Amsterdam 1950).
2. T. W. Goodwin, The Comparative Biochemistry of the Carotenoids (Chapman and Hall, London 1952); 2nd Ed. in preparation.
3. L. Zechmeister, Cis-trans Isomeric Carotenoids, Vitamins A and Arylpolyenes (Springer, Vienna 1962).
4. National Academy of Sciences, Specifications and Criteria for Biochemical Compounds, 2nd Ed., Nat. Acad. Sci.-Nat. Res. Counc, Publ. No. 1344 (Washington D.C. 1967); Supplements in the press.
5. H. Braconnot (paprika), Ann. Chim. Phys. [2] 6, 122 (1817)