Do you mean they are self referencing as follows:
select t4.name as town,
t3.name as county,
t2.name as district,
t1.name as admin1,
from geoname t0
left join geoname t1 on t1.admin1 = t0.admin1 and t1.feature_code = 'ADM1'
left join geoname t2 on t2.admin2 = t0.admin2 and t2.feature_code = 'ADM2'
left join geoname t3 on t3.admin3 = t0.admin3 and t3.feature_code = 'ADM3'
left join geoname t4 on t4.admin4 = t0.admin4 and t4.feature_code = 'ADM4'
where t0.name = 'London'
It would help if the documentation was updated as it doesn't make this clear?