US Patent No. 35454522
US Patent No. 84584464
US Patent No. 66211513
US Patent No. 5215485
US Patent No. 12786451
US Patent No. 47585476
US Patent No. 1678451
US Patent No. 25456441
US Patent No. 1784512
US Patent No.84485456
US Patent No. 56584714
US Pate 89285
Patent No.
82875154
US Patent No. 10151784
US Patent No. 71548713
US Patent No. 54653148
US Patent No. 4548411225
US Patent 4531548