With no explanation, label each line with "O", "other-chemicalthing", "other-biologything", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart" or "building-airport" preceded by ":".
Nitrous
oxide
potentiating
the
haematological
toxicity
of
methotrexate
has
also
been
documented
.
Nitrous:other-chemicalthing
oxide:other-chemicalthing
potentiating:O
the:O
haematological:O
toxicity:O
of:O
methotrexate:other-biologything
has:O
also:O
been:O
documented:O
.:O