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| 5867226 | Wehmeyer et al. | Feb 1999 | |
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| Number | Date | Country |
|---|---|---|
| 721253A2 | Jul 1996 | EP |
| 774866A2 | May 1997 | EP |
| WO 8302208 | Feb 1982 | WO |
| WO9501057 | Jan 1995 | WO |
| WO9631980 | Oct 1996 | WO |
| WO9812875 | Mar 1998 | WO |
| Entry |
|---|
| “PBS Enterprises” press release, Sep. 11, 1990. |