M Walsh, E Stein, MC Kelly, P Velagaleti - US Patent 9,426,599, 2016 - Google Patents
3,809,811 4,107.465 4,284,847 4476, 724 4,862.505 4,868,880 5,033,086 5.438, 623
5,737,389 5,785,661 5,825,894 5,870,481 6,086,541 6,109,107 6,144,747 6,167,138 6.212 …