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3791618 | Nelson et al. | Feb 1974 | A |
4327891 | Allen et al. | May 1982 | A |
5150877 | Whiteside et al. | Sep 1992 | A |
5295655 | Wilson et al. | Mar 1994 | A |
5335694 | Whiteside | Aug 1994 | A |
5649686 | Wilson | Jul 1997 | A |
5865420 | Wilson | Feb 1999 | A |