With no explanation, label each line with "organization-media/newspaper", "art-broadcastprogram", "O", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
He
is
also
a
frequent
narrator
on
PBS
television
'
s
``
Nature
``
series
.
He:O
is:O
also:O
a:O
frequent:O
narrator:O
on:O
PBS:organization-media/newspaper
television:organization-media/newspaper
':organization-media/newspaper
s:O
``:O
Nature:art-broadcastprogram
``:O
series:O
.:O