With no explanation, label each line with "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport", "building-hospital" or "building-hotel" preceded by ":".
However
,
a
second
national
conference
was
held
in
March
1973
.
However:O
,:O
a:O
second:O
national:O
conference:O
was:O
held:O
in:O
March:O
1973:O
.:O