With no explanation, label each line with "O", "person-politician", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
He
was
unconditionally
released
by
President
F.
W.
de
Klerk
in
1988
.
He:O
was:O
unconditionally:O
released:O
by:O
President:O
F.:person-politician
W.:person-politician
de:person-politician
Klerk:person-politician
in:O
1988:O
.:O