
theorem :: THEOREM 4.18. (2) iff (5)
  for L be Boolean LATTICE holds L is arithmetic iff L is continuous & L
  opp is continuous
proof
  let L be Boolean LATTICE;
  thus L is arithmetic implies L is continuous & L opp is continuous by Th9,
YELLOW_7:38;
  assume that
A1: L is continuous and
A2: L opp is continuous;
  L is completely-distributive by A1,A2,WAYBEL_6:39;
  then
  for x be Element of L ex X be Subset of L st X c= ATOM L & x = sup X by Lm5;
  then ex X be set st L,BoolePoset X are_isomorphic by A1,Lm6;
  hence thesis by Th10,WAYBEL_1:6;
end;
