Doctors are performing surgery.
The surgeons performed emergency surgery on the President.
The surgery may have been a scheduled elective surgery and not an emergency surgery.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_surgery(x2) & n_doctor(x1))
exists e1 x1 x2 x3 x4.(ne_nam_president(x4) & n_surgeon(x1) & on(e1,x4) & Theme(e1,x2) & Actor(e1,x1) & v_perform(e1) & n_surgery(x2) & of(x2,x3) & n_emergency(x3))