Abo-Shaeer, Jamil R. (July 2010). "Negative-Index Materials". DARPA – Defense Science Offices (DSO). Archived from the original(Public Domain – Information presented on the DARPA Web Information Service is considered public information and may be distributed or copied.) on 2010-12-24. Retrieved 2010-07-05.
doi.org
Negative permitivitty was explored in group of research papers which included:
Smith, David; Schultz, Sheldon; Kroll, Norman; Shelby, Richard A. "Left handed composite media" U.S. patent 6,791,432
Publication date 2001-03-16, Issue date 2004-03-14.
Abo-Shaeer, Jamil R. (July 2010). "Negative-Index Materials". DARPA – Defense Science Offices (DSO). Archived from the original(Public Domain – Information presented on the DARPA Web Information Service is considered public information and may be distributed or copied.) on 2010-12-24. Retrieved 2010-07-05.