With no explanation, label each line with "O", "other-chemicalthing", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
Chromocene
is
structurally
similar
to
ferrocene
,
the
prototype
for
the
metallocene
class
of
compounds
.
Chromocene:other-chemicalthing
is:O
structurally:O
similar:O
to:O
ferrocene:other-chemicalthing
,:O
the:O
prototype:O
for:O
the:O
metallocene:other-chemicalthing
class:O
of:O
compounds:O
.:O