Figure 8
From: Applying Physical-Layer Network Coding in Wireless Networks
An example of a dual packing, where flow 1 and flow 2 belong to the clockwise unidirectional packing, flow 3 and flow 4 belong to the counterclockwise unidirectional packing. The white nodes are nonresidual nodes, the red nodes are the residual nodes of the clockwise unidirectional packing, the green nodes are the residual nodes of the counterclockwise packing, and the blue nodes are the residual nodes of both the two unidirectional packings. The nodes in the rectangles are the uncommon nodes.