| Number | Name | Date | Kind |
|---|---|---|---|
| 890259 | Callanan | Jun 1908 | |
| 2504650 | Chessrown | Oct 1950 | |
| 3574957 | Bello-Bridick | Apr 1971 | |
| 3899838 | Lalley et al. | Aug 1975 | |
| 4173833 | Rosenblatt | Nov 1979 | |
| 4690409 | Scalia | Sep 1987 | |
| 4968255 | Lee et al. | Nov 1990 | |
| 5161976 | Crowe | Nov 1992 | |
| 5427529 | Dunse | Jun 1995 | |
| 5484287 | Concepcion-Diaz | Jan 1996 | |
| 5571019 | Wilson | Nov 1996 |
| Entry |
|---|
| Classrooms That Work, Second Edition, by Patricia Cunningham and Richard Allington, Copyright 1999. pp. 65-66, ISBN 0-321-01339-5. |
| Summit Learning Math catalog, p. 30, Clever Catch Balls. |