\Graph {3cm,2}{3cm,4} \Line (0,0) (0,4) <{f(z,s)} \Line (0,4) (2,4) ^{H(z,t)} \Line (0,0) (2,0) _{*} \Line (2,0) (2,4) \Line (0,4) (2,2) _{\;\;H(z,0) = f(z,1)} \ro \endGraph