theorem Th18:
  for F,G being strict finite Group st card F = p & card G = p & p
  is prime holds F,G are_isomorphic
proof
  let F,G be strict finite Group;
  assume that
A1: card F = p & card G = p and
A2: p is prime;
  F is cyclic Group & G is cyclic Group by A1,A2,GR_CY_1:21;
  hence thesis by A1,Th17;
end;
