| Number | Name | Date | Kind |
|---|---|---|---|
| 895875 | Mercer | Aug 1908 | |
| 1555937 | Billman | Oct 1925 | |
| 1564746 | Barnard | Dec 1925 | |
| 1674533 | Templeton | Jun 1928 | |
| 3531122 | Peebles | Sep 1970 | |
| 3609886 | Vien | Oct 1971 | |
| 4138120 | Daitzman | Feb 1979 | |
| 4468036 | Istrati | Aug 1984 |
| Number | Date | Country |
|---|---|---|
| 2654115 | Jun 1977 | DEX |
| Entry |
|---|
| Stephen Krulik, "Problems, Problem Solving, and Strategy Games", pp. 649-652 of Nov. 1977 Mathematics Teacher. |