With no explanation, label each line with "O", "product-train", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
The
trains
were
named
``
Keystone
Service
``
in
1981
.
The:O
trains:O
were:O
named:O
``:O
Keystone:product-train
Service:product-train
``:O
in:O
1981:O
.:O