In Berlin, the <e1>communists</e1> threw up a <e2>wall</e2> of barbed wire and stone to block the exit of freedom-seeking Germans.
In Berlin, the communists
In Berlin, the communists threw up a wall of barbed wire and stone to block the exit of freedom-seeking Germans.
<triplet> communists <subject> wall <object> Product-Producer(e2,e1)