1. P. Karrer and E. Jucker, Carotinoide (Birkhäuser, Basle 1948).
2. P. Karrer and E. Jucker, Carotenoids, English translation by E.A. Braude (Elsevier, Amsterdam 1950).
3. T.W. Goodwin, The Comparative Biochemistry of the Carotenoids (Chapman and Hall, London 1952).
4. L.R. Blinks, in Autotrophic Microorganisms (4th Symp. Soc. Gen. Microbiol.) (Cambridge University Press, Cambridge 1954), p. 224.
5. J.H. Burnett, in Chemistry and Biochemistry of Plant Pigments, ed. by T.W. Goodwin (Academic Press, London 1965), p. 381.