theorem Th87:
  for N1,N2 being strict StableSubgroup of G st N1 is normal
  StableSubgroup of H1 & N2 is normal StableSubgroup of H1 holds N1 "\/" N2 is
  normal StableSubgroup of H1
proof
  let N1,N2 be strict StableSubgroup of G;
  assume
A1: N1 is normal StableSubgroup of H1 & N2 is normal StableSubgroup of H1;
  then reconsider N19=N1,N29=N2 as StableSubgroup of H1;
  N1 "\/" N2 = N19 "\/" N29 by Th86;
  hence thesis by A1,Th32;
end;
