
theorem Th16: :: AChain0:
for R being RelStr, A being StableSet of R, B being Subset of A
 holds B is StableSet of R
proof
 let R be RelStr, A be StableSet of R, B be Subset of A;
 reconsider BB = B as Subset of R by XBOOLE_1:1;
 BB is stable by Def2;
 hence thesis;
end;
