| Number | Name | Date | Kind |
|---|---|---|---|
| 2938304 | Thomas et al. | May 1960 | |
| 3469342 | Morris | Sep 1969 | |
| 3697026 | Hambrick | Oct 1972 | |
| 4060934 | Skaggs et al. | Dec 1977 | |
| 4372100 | Miller et al. | Feb 1983 | |
| 4827666 | Tweddell, IV | May 1989 | |
| 4850137 | Foster | Jul 1989 | |
| 4930252 | Krause et al. | Jun 1990 | |
| 4997176 | Spinosa | Feb 1991 | |
| 5054236 | Sands | Oct 1991 | |
| 5076009 | Cibor | Dec 1991 | |
| 5099872 | Tarvin et al. | Mar 1992 | |
| 5157868 | Munoz | Oct 1992 | |
| 5279071 | McDougall | Jan 1994 | |
| 5358000 | O'Hair | Oct 1994 |
| Entry |
|---|
| Wordless Workshop Popular Science Dec., 1978 p. 140. |