Parents.
4,668,055; 4,668,056; 4,671,623; 4,672,187; 4,684,206; 4,703,469; 4,704,718; 4,718,052; 4,719,614; 4,729,122; 4,730,896; 4,731,772; 4,731,786; 4,742,522; 4,744,071; 4,744,073; 4,750,819; 4,752,931; 4,753,524; 4,756,583; 4,759,611; 4,759,612; 4,759,614; 4,761,046; 4,761,058; 4,761,548; 4,766,597; 4,769,805; 4,772,118; 4,774,702; 4,780,879; 4,782,491; 4,783,133; 4,783,134; 4,783,589; 4,783,788; 4,784,447; 4,787,089; 4,791,584; 4,792,207; 4,793,670; 4,793,672; 4,793,687; 4,795,240; 4,795,907.