f (x, y) =\ sum_ {k=1} ^ {\ infty}\ left [f_ {k} (x) -f_ {k+1} (x)\ right] f_ {k} (y); \ int_ {Y}\ int_ {X} f d n d m=0\ neq 1=\ int_ {Y}\ int_ {X} f d m d n. Demostrar que siϕ1 esm -int...f (x, y) =\ sum_ {k=1} ^ {\ infty}\ left [f_ {k} (x) -f_ {k+1} (x)\ right] f_ {k} (y); \ int_ {Y}\ int_ {X} f d n d m=0\ neq 1=\ int_ {Y}\ int_ {X} f d m d n. Demostrar que siϕ1 esm -integrable onX yϕ2 esn -integrable onY, entoncesf esp -integrable onX×Y y yfk=fCHk, asífk son P∗-simple (de ahí mapas Fubini), yfk→f (punto sabio) enX×Y, con|fk|≤|f| y