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 ":".
The
maintenance
of
such
arrest
in
the
G2
phase
is
further
sustained
by
p53
and
p21
.
The:O
maintenance:O
of:O
such:O
arrest:O
in:O
the:O
G2:other-biologything
phase:O
is:O
further:O
sustained:O
by:O
p53:other-biologything
and:O
p21:other-chemicalthing
.:O