Fig. 3.

Graphical models illustrating identification of $Q=P\left(y|do\left(x\right)\right)$ through the use of experiments over an auxiliary variable Z. Identifiability follows from $P\left(x,y|do\left(Z=z\right)\right)$ in A, and it also requires $P\left(v\right)$ in B. Identifiability in models A and B follows from the identifiability of Q in $G_{\overline{Z}}$.