A group of doctors performing surgery on a patient.
Nobody is performing surgery.
Their is either a group of doctors performing surgery or nobody is performing surgery for it can not be both.
exists e1 x1 x2 x3 x4 x5.(a_topic(x1) & on(e1,x5) & n_patient(x5) & Theme(e1,x4) & Actor(e1,x3) & v_perform(e1) & n_surgery(x4) & (x1 = x3) & of(x1,x2) & n_doctor(x2) & n_group(x1))
-exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_surgery(x2) & n_person(x1))