| Number | Name | Date | Kind |
|---|---|---|---|
| 4300967 | Sigl | Nov 1981 | |
| 4450026 | Pieniak et al. | May 1984 | |
| 4595441 | Holvoet et al. | Jun 1986 | |
| 4662877 | Williams | May 1987 | |
| 4704115 | Buell | Nov 1987 | |
| 4704116 | Enloe | Nov 1987 | |
| 4738677 | Foreman | Apr 1988 | |
| 4753646 | Enloe | Jun 1988 | |
| 4846823 | Enloe | Jul 1989 | |
| 4990147 | Freeland | Feb 1991 | |
| 4992125 | Suzuki et al. | Feb 1991 | |
| 5034007 | Igaue et al. | Jul 1991 | |
| 5061261 | Suzuki et al. | Oct 1991 | |
| 5110386 | Ochi et al. | May 1992 |
| Number | Date | Country |
|---|---|---|
| 3286761 | Dec 1991 | JPX |
| Entry |
|---|
| "Ultra 1992--Preliminary R&D Overview of Timing, PPD Steps, Features, Approaches and Issues," Heinz Pieniak, May 13, 1991. |