With no explanation, label each line with "O", "organization-company", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
Braathens
Helikopter
operated
from
1989
to
1993
,
after
which
it
was
sold
to
and
merged
with
the
main
competitor
,
Helikopter
Service
.
Braathens:organization-company
Helikopter:organization-company
operated:O
from:O
1989:O
to:O
1993:O
,:O
after:O
which:O
it:O
was:O
sold:O
to:O
and:O
merged:O
with:O
the:O
main:O
competitor:O
,:O
Helikopter:organization-company
Service:organization-company
.:O