1. Alicino, J. F.: Iodometric methods for the assay of penicillin preparations. Anal. Chem. 18, 619?620 (1946)
2. Van Baalen, C.: Studies on marine blue-green algae. Bot. Mar. 4, 129?139 (1962)
3. Citri, N., Pollock, M. R.: The biochemistry and function of ?-lactamase (penicillinase). Advanc. Enzymol. 28, 237?323 (1966)
4. Fay, P., Lang, N. J.: The heterocysts of blue-green algae. I. Ultrastructural integrity after isolation. Proc. roy. Soc. B 178, 185?192 (1971)
5. Fogg, G. E., Stewart, W. D. P., Fay, P., Walsby, A. E.: The blue-green algae. London-New York: Academic Press 1973