reserve G for Graph,
  v, v1, v2 for Vertex of G,
  c for Chain of G,
  p, p1, p2 for Path of G,
  vs, vs1, vs2 for FinSequence of the carrier of G,
  e, X for set,
  n, m for Nat;

theorem Th11: :: see MSSCYC_1:4
  for s, t being Vertex of G st s = (the Source of G).e & t = (the
  Target of G).e holds <*t, s*> is_vertex_seq_of <*e*>
proof
  let s, t be Element of the carrier of G;
  assume
A1: s = (the Source of G).e & t = (the Target of G).e;
  set c = <*e*>;
  set vs = <*t, s*>;
A2: vs/.(1+1) = s by FINSEQ_4:17;
A3: len c = 1 by FINSEQ_1:39;
  hence len vs = len c + 1 by FINSEQ_1:44;
  let n be Nat;
  assume 1<=n & n<=len c;
  then
A4: n = 1 by A3,XXREAL_0:1;
  c.1 = e & vs/.1 = t by FINSEQ_4:17;
  hence thesis by A1,A4,A2;
end;
