With no explanation, label each line with "O", "event-attack/battle/war/militaryconflict", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
It
has
been
discussed
since
at
least
1979
when
a
book
was
published
relating
to
the
Vietnam
War
.
It:O
has:O
been:O
discussed:O
since:O
at:O
least:O
1979:O
when:O
a:O
book:O
was:O
published:O
relating:O
to:O
the:O
Vietnam:event-attack/battle/war/militaryconflict
War:event-attack/battle/war/militaryconflict
.:O