With no explanation, label each line with "location-GPE", "O", "organization-religion", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart" or "building-airport" preceded by ":".
In
the
middle
of
the
19th
century
the
national
affiliation
of
the
Orthodox
Slavs
of
Macedonia
became
the
locus
of
a
contest
between
Greeks
and
Bulgarians
,
who
intensified
their
national
educational
activity
in
the
region
,
alongside
with
Serbia
.
In:O
the:O
middle:O
of:O
the:O
19th:O
century:O
the:O
national:O
affiliation:O
of:O
the:O
Orthodox:organization-religion
Slavs:organization-religion
of:O
Macedonia:location-GPE
became:O
the:O
locus:O
of:O
a:O
contest:O
between:O
Greeks:location-GPE
and:O
Bulgarians:location-GPE
,:O
who:O
intensified:O
their:O
national:O
educational:O
activity:O
in:O
the:O
region:O
,:O
alongside:O
with:O
Serbia:location-GPE
.:O