| Number | Name | Date | Kind |
|---|---|---|---|
| 3506268 | Stadler | Apr 1970 | |
| 3709497 | Barlow | Jan 1973 | |
| 3865381 | Hayes | Feb 1975 | |
| 3871659 | Breslow et al. | Mar 1975 | |
| 4061335 | Breslow | Dec 1977 | |
| 4067576 | Balos et al. | Jan 1978 | |
| 4244579 | Campos | Jan 1981 |
| Entry |
|---|
| Games and Puzzles Magazine "The Bermuda Triangle" p. 28, 9/1977. |