reserve n,m,i,j,k for Nat,
  x,y,e,X,V,U for set,
  W,f,g for Function;
reserve p,q for FinSequence;
reserve G for Graph,
  pe,qe for FinSequence of the carrier' of G;

theorem
  i in dom pe implies (the Source of G).(pe.i) in the carrier of G & (
  the Target of G).(pe.i) in the carrier of G by FINSEQ_2:11,FUNCT_2:5;
