let T be non empty TopSpace; :: thesis:
assume A1: ( T is sober & T is locally-compact ) ; :: thesis:
let F be Subset-Family of T; :: according to WAYBEL12:def 6 :: thesis:
assume that
A2: F is countable and
A3: for S being Subset of T st S in F holds
( S is open & S is dense ) ; :: thesis:
A4: F is open by A3;
for X being Subset of T st X in F holds
X is dense by A3;
then A5: ( F is open & F is dense ) by A4;
reconsider I = Intersect F as Subset of T ;
take I ; :: thesis:
thus I = Intersect F ; :: thesis:

suppose A6: F <> {} ; :: thesis:

for Q being Subset of T st Q <> {} & Q is open holds
Intersect F meets Q

let Q be Subset of T; :: thesis:
assume that
A7: Q <> {} and
A8: Q is open ; :: thesis:
consider S being irreducible Subset of T such that
A9: for V being Subset of T st V in F holds
S /\ Q meets V by A1, A2, A5, A6, A7, A8, Th43;
consider p being Point of T such that
A10: p is_dense_point_of S and
for q being Point of T st q is_dense_point_of S holds
p = q by A1;
S is closed by YELLOW_8:def 3;
then A11: S = Cl {p} by A10, YELLOW_8:16;
A12: for Y being set st Y in F holds
( p in Y & p in Q )

let Y be set ; :: thesis:
assume A13: Y in F ; :: thesis:
then reconsider Y1 = Y as Subset of T ;
S /\ Q meets Y1 by A9, A13;
then A14: (S /\ Q) /\ Y1 <> {} ;

assume not p in Q /\ Y1 ; :: thesis:
then p in (Q /\ Y1) ` by XBOOLE_0:def 5;
then {p} c= (Q /\ Y1) ` by ZFMISC_1:31;
then A15: Cl {p} c= Cl ((Q /\ Y1) `) by PRE_TOPC:19;
Y1 is open by A3, A13;
then Q /\ Y1 is open by A8;
then (Q /\ Y1) ` is closed ;
then S c= (Q /\ Y1) ` by A11, A15, PRE_TOPC:22;
then S misses Q /\ Y1 by SUBSET_1:23;
then S /\ (Q /\ Y1) = {} ;
hence contradiction by A14, XBOOLE_1:16; :: thesis:

end;

hence ( p in Y & p in Q ) by XBOOLE_0:def 4; :: thesis:

end;

then for Y being set st Y in F holds
p in Y ;
then A16: p in Intersect F by SETFAM_1:43;
ex Y being object st Y in F by A6, XBOOLE_0:def 1;
then p in Q by A12;
then (Intersect F) /\ Q <> {} by A16, XBOOLE_0:def 4;
hence Intersect F meets Q ; :: thesis:

end;

hence I is dense by TOPS_1:45; :: thesis:

end;

suppose F = {} ; :: thesis:

then Intersect F = [#] T by SETFAM_1:def 9;
hence I is dense ; :: thesis:

end;

end;