theorem Th51:
  for p being PartState of S, k being Nat
  holds DataPart IncIC(p,k) = DataPart p
proof
  let p be PartState of S, k be Nat;
  thus DataPart IncIC(p,k)
  = DataPart p +* DataPart Start-At(IC p+k,S) by FUNCT_4:71
    .= DataPart p +* {} by Th20
    .= DataPart p;
end;
