With no explanation, label each line with "O", "person-artist/author", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
However
,
while
Courbet
used
a
more
even
surface
,
Achenbach
's
painting
was
more
relief-like
.
However:O
,:O
while:O
Courbet:person-artist/author
used:O
a:O
more:O
even:O
surface:O
,:O
Achenbach:person-artist/author
's:O
painting:O
was:O
more:O
relief-like:O
.:O