With no explanation, label each line with "location-GPE", "O", "building-airport", "location-other", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting" or "art-writtenart" preceded by ":".
In
addition
,
there
are
several
independent
airports
serving
London
,
including
Heathrow
,
the
busiest
airport
in
Europe
.
In:O
addition:O
,:O
there:O
are:O
several:O
independent:O
airports:O
serving:O
London:location-GPE
,:O
including:O
Heathrow:building-airport
,:O
the:O
busiest:O
airport:O
in:O
Europe:location-other
.:O