1. 1. P. M. Bradley, I. W. Schwemmler, and H. E. A. Schenk, 1980 .InEndocytobiology : 515 -522 . de Gruyter. Berlin, FRG.
2. 2. P. M. Bradley, 1984 . PhD. Thesis . Worcester Polytechnic Institute. Worcester, Mass. (University Microfilm International 84-07038.).
3. Uptake of cyanobacteria contained in oil drops by plant protoplasts
4. 4. P. M. Bradley, W. Schwemmler, and H. E. A. Schenk, 1983 .InEndocytobiology II . : 613 -621 . de Gruyter. Berlin, FRG.
5. Introduction of a nitrogen-fixing cyanobacterium into tobacco shoot regenerates