Helicity and Electomagnetic Field Topology

Helicity and Electromagnetic Field Topology is a chapter in Advanced Electromagnetism: Foundations, Theory and Applications, edited by Terence W. Barrett and Dale M. Grimes (World Scientific, 1995).

Link to the book:

http://books.google.com/books/about/Advanced_Electromagnetism.html?id=lA8tgLMRu2kC