1. Ledain JE, Colgrove JA, Koren D (1999) U.S. Patent No. 5,996,054. U.S. Patent and Trademark Office, Washington, DC
2. Yanai M, Vishlitzky N, Alterescu B, Castel D, Shklarsky GG, Ofek Y (2007) U.S. Patent No. 7240238 B2. U.S. Patent and Trademark Office, Washington, DC
3. Blumenau SM, Raz Y (2002) U.S. Patent No. 6,421,711. U.S. Patent and Trademark Office, Washington, DC
4. Zheng J, Jiang X, Vahalia U (2003) U.S. Patent No. 6,571,259. U.S. Patent and Trademark Office, Washington, DC
5. Scherr AL (2006) U.S. Patent No. 7,134,138. U.S. Patent and Trademark Office, Washington, DC