reserve phi,fi,psi for Ordinal-Sequence,
  A,A1,B,C,D for Ordinal,
  f,g for Function,
  X for set,
  x,y,z for object;
reserve f1,f2 for Ordinal-Sequence;

theorem
  1 in C & A <> {} implies 1 in exp(C,A)
proof
  assume that
A1: 1 in C and
A2: A <> {};
  exp(C,{}) = 1 by ORDINAL2:43;
  hence thesis by A1,A2,Th24,ORDINAL3:8;
end;
