N. Behdad, K. Sarabandi, “Improved slot and wire loop antennas", IEE proceedings; Microwave, Antennas and Propagation, Volume: 153  Issue: 3, June 2006, Page(s):  287- 292

The publication is available to download from http://ieeexplore.ieee.org/xpl/tocresult.jsp?isnumber=34376&isYear=2006