With no explanation, label each line with "art-writtenart", "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "building-airport", "building-hospital" or "building-hotel" preceded by ":".
He
left
the
Washington
Post
and
focused
on
researching
and
writing
Modern
History
,
especially
military
history
non-fiction
.
He:O
left:O
the:O
Washington:art-writtenart
Post:art-writtenart
and:O
focused:O
on:O
researching:O
and:O
writing:O
Modern:art-writtenart
History:art-writtenart
,:O
especially:O
military:O
history:O
non-fiction:O
.:O