With no explanation, label each line with "O", "product-weapon", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
An
Oerlikon
20
mm
cannon
was
placed
on
the
top
of
the
tower
for
anti-aircraft
purposes
.
An:O
Oerlikon:product-weapon
20:product-weapon
mm:product-weapon
cannon:product-weapon
was:O
placed:O
on:O
the:O
top:O
of:O
the:O
tower:O
for:O
anti-aircraft:O
purposes:O
.:O