reserve x,y,z for object,X,Y for set;
reserve N for e_net;
reserve N for e_net;

theorem Th33:
  ((the entrance of N) \ id(the carrier of N))~ c=
    [:e_Places(N), e_Transitions(N):] &
  ((the escape of N) \ id(the carrier of N))~ c=
    [:e_Places(N),e_Transitions(N):]
proof
  (the entrance of N) \ id(the carrier of N) c=
    [:e_Transitions(N),e_Places N :] &
  (the escape of N) \ id(the carrier of N) c=
    [:e_Transitions(N),e_Places N:] by Th18;
  hence thesis by SYSREL:4;
end;
