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| 8-210828 | Aug 1996 | JPX |
| Number | Name | Date | Kind |
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| 5710915 | McElhiney et al. | Jan 1998 |
| Number | Date | Country |
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| 7-271825 | Oct 1995 | JPX |
| Entry |
|---|
| An Introduction to Database Systems, vol. I, Fourth Edition, Addison-Wesley Publishing Company, "Built-In Functions", pp. 136-139, 1986. |