| Number | Name | Date | Kind |
|---|---|---|---|
| 3640496 | Duncan | Feb 1972 | |
| 4923158 | Saisho | May 1990 | |
| 5007607 | Kim | Apr 1991 | |
| 5088669 | Zinnbauer | Feb 1992 | |
| 5312078 | Marsh | May 1994 | |
| 5568708 | Kassardjian et al. | Oct 1996 | |
| 5697669 | Yemini | Dec 1997 |
| Entry |
|---|
| PI, Inc. Advertisement; Undated, admitted prior art. |