1. W. Lietzmann, “Visual Topology,” Chatto & Windus Ltd., London (1962).
2. B. H. Arnold, “Intuitive concepts in elementary topology,” Prentice-Hall Inc., Englewood Cliffs, New Jersey (1962).
3. R. Thorn, “Stabilité structurelle et morphogénese. Essai d’une théorie générale des modéles,” W. A. Benjamin, Inc., Reading, Massachussets (1972).
4. P. Pinto da Silva and M. L. Nogueira, Membrane fusion during secretion; a hypothesis based on electron microscopic observation of Phytophthora palmivora zoospores during encystment, J. Cell. Biology 73:161(1977).
5. D. Shotton, Freeze-fracture view of membrane fusion, Nature 272:16 (1978).