Alford Antenna Information

Hello,

I have to design an Alford Loop antenna and I can not find information about design. Even theoretical information is not very easy to get. Does anyone have some information that may share?

Thanks a lot.

http://www.qsl.net/n1bwt/ch7_part4.pdf
http://www.qsl.net/kd2bd/slot.html
http://www.freepatentsonline.com/5767809.pdf